One of the programmers for several of the Ultima games, Mike McShaffry, in his book "Game Coding Complete" mentions a bug which caused a spell to produce a wall of fire. They then decided they liked this and decided to leave it in.
Ultima VII Part II: Serpent Isle had a copious amount of bugs, due to the rushed completion. The most noteworthy ones are the "False Coin" spell, which is supposed to make illusionary money but fails at the "illusionary" part, "Vibrate" which doesn't do damage but makes people drop all their possessions (including some things they're not supposed to drop) and "Serpent Bond", which allows you to bypass script triggers. This can be used to, among other things, carry stuff out of a dream, and save a temporary party member from his scripted death.
Its predeccessor, Ultima VII: The Black Gate, was also full of bugs, and one of the more useful ones involved Batlin's delivery request in Britain. With the right usage of declining his request, accepting his request, and dumping part of your inventory, you could repeatably gain 100 EXP and dupe any item of yours that can stack.
Ultima VII: The Black Gate also had diapers. As, apparently, a joke item, they made enemies repelled by dirty diapers. Then the programmers forgot to make any creature resistant to diaper-repulsion, with the result that a pile of dirty diapers is one of the most effective weapons in the game.
Ultima Online had a rather famous incident of "it's not a bug it's a feature". A "creative use of magic" allowed someone to loot people's houses. Essentially robbing someone of all of their stored possessions.
In the beta Lord British came onto the server himself to talk to players about a recent crash. Unbeknown to him or anyone else, the crash had turned off his "Invincible" tag. Some player spontaneously decided to cast a fire spell on him as a joke. So spontaneously, in fact, that he had to steal the scroll from someone watching the speech. He wound up assassinating Lord British in full view of everyone..
As bizarre as it may sound for what would now be considered a simple act of PVP on a dev who didn't realize his power was turned off, at the time this was a really big deal. There were articles about this event in mainstream PC gamer magazines, interviews with the perp in question ('Aquaman') and more - it turned into a huge debate over PK-ing, the act of 'Player Killing', whether or not it was fair and what could be done about it. The article in PC Gamer magazine itself treated PKing as a threat to the average gamer and something that could turn people away from this relatively new genre of game. Re-reading these old articles is exactly as quaint as you'd imagine, proto-MMO'ers 'discussing' (read: arguing bitterly over) what could be done about what would eventually become one of the largest draws to the MMO market, PVP.
Once upon a time there were a lot of item duplication bugs in Ultima Online, that could dupe all kinds of things, like scrolls that cast a magic arrow for 1 pt of damage. There were also slimes that would split in half every time they took damage. One enterprising player wrote up a script, barricaded himself behind some boxes, and promptly crashed the server.
You can save the hardest-to-find spell components from being consumed simply by dragging them back into your inventory after the text box pops up to input the name of the spell. The same piece of nightshade for every spell that needs it? You bet!
A few of the bosses could be targeted and killed with ranged weapons before their scripted cutscenes kicked in. They wouldn't move to defend themselves, and after they were killed you could trigger the cutscene and it would go off as scripted — minus the boss.
The dungeon Wrong would take away all your items if you were caught by the guards. You could easily get them back once you knew where they were stored, but if you had filled all of your available inventory slots (anything would do) the game would put your original items in a bag for you. The key here being that bags are extremely rare (without the 'economy' patch which actually gives you something to do with the piles of gold you invariably leave scattered around), giving you nine slots for the price of one. This bug could be repeated until your backpack was filled with bags.
Stacking "bridges": With a Level 0 spell, a little ingenuity, and a lot of grabbing everything that's not nailed down, you could make items literally float in midair and due to the mechanics of the game, you could hoist yourself up onto them. Given enough time and effort (but still far less than getting there normally) you could access parts of the game that normally wouldn't be arrived at until much later.
Since every item in the game, even money, was a physical object, sometimes they would clip out of whatever they were stored in. One chest in particular had a piece of the best armor in the game that could only be unlocked with a key gained by starting the game as one particular class. But find the right patch of pixels and it was yours for the taking anyway.
Pulling out a Glass Sword in the Buccaneer's Den armor and weapons shop would make the glass of the display cases disappear, giving you access to some really good gear that you weren't supposed to get.
Dark Souls Pre 1.04 had a pretty crazy exploit that involved the Dragon Stone you get for joining the path of dragons covenant that could net you infinite souls and humanity while using it.
Some bugs carry over, including the very useful Bottomless Box Glitch, transferring any items, including plot-relevant ones to a freshly-starting character, allowing them to roll (literally) with fully upgraded items. This makes for a tremendous benefit to returning players who want to get their leveling from the get go immediately and stat their perfect build from early on, but also of a boon for Griefers to invade other people at extremely low levels.
Star Control 2 had the infamous "planet-lander" bug: In the original version, selling your planet-lander when you had none to sell would cause an underflow bug, leaving you with around two million or so planet landers, that you could then sell for cash.
The Elder Scrolls III: Morrowind has a bug with alchemy that can quickly prove to be a gamebreaker, on two fronts. First, while simple alchemy ingredients are available in unlimited supply for 1 gold each, the potion created by combining two of these ingredients with alchemy sells for substantially more than 2 gold, making for a source of unlimited money right from the start of the game. Second, the potency of potions is partially based on your intelligence score, which can be boosted by an effect called Fortify Intelligence... and it just so happens that you can find the ingredients to make Fortify Intelligence potions in unlimited supply in the first major city you reach in the game. By creating potions, drinking them, and creating more potions, the player could easily create potions of horrifying power (boosting statistics by tens of thousands of points, or restoring thousands of points of health per second for literally days) within minutes of starting the game. Combined with the first alchemy bug, the money needed to buy these ingredients was no object... the free master alchemy set lying around for the taking in the mage's guild of another town only made it easier.
Another bug often combined with the one above was selling items to a merchant with a negative quantity. Merchants designated in the editor with a negative quantity for an item would regenerate that number after you left the dialogue box. So a merchant with -20 Muck Root always had 20 Muck Root when you re-entered the menu. The trick is that if you sell that item to them, it would instead create an even more negative quantity. So, with the above, if you bought the 20 Muck Root, exited, then re-entered and sold them the 20, they'd then have 40 to sell every time you entered the menu and so on. Thus, you had an infinite supply of any item that started with a negative value. One of the primary uses was stacking common potion ingredients to grind your alchemy skill.
By 'juggling' weapons that grant stat bonuses, it's possible to have the effect stack with itself and render you nigh-godlike. This allows you to complete the game in a matter of minutes.
The hero could shoot arrows through closed doors to overcome staggering odds.
Alternatively, once you owned the spell Soul Trap, (or a piece of equipment that would cast it,) and a spell to fortify an attribute, you could create a spell to fortify your strength/speed/intelligence etc. for one second and then soul trap yourself to permanently apply the fortification. Doing so could allow you to increase your attributes, skills, etc far beyond the scope the game would normally allow, and make it so you could jump over Red Mountain or cross Vvardenfell on foot in a matter of minutes.
This works with spells other than fortify attribute, as well. Combining it with a spell to summon a golden saint, for instance, will summon a permanent golden saint to run around with. This can be done multiple times, to either slaughter them and take their gear or to stomp around followed by an army.
Another endless gold trick involves selling gold pieces to merchants. Clicking the gold to sell it one piece at a time, then taking it all back at once, will result in the merchant buying it for face value then giving it back at a bulk discount. You can't have a transaction without buying or selling anything, though, so the end result can be selling one gold piece for as much as you have the patience for.
A bug lets you duplicate any object hundreds of times. Cue Youtube videos of players flooding cities knee-deep in watermelons and human hearts.
Make two copies of an enchanted wearable item. Equip one copy. Duplicate the unworn one. Both fall off, but the effect remains. Change clothing on another body part to make it permanent. Stack enchants to your heart's content. Alternatively, just be wearing enchanted items during one of the few moments where the game forcibly removes your gear.
Also: paintbrushes aren't affected by gravity, allowing you to construct stairways, sniper's nests, and so forth out of dropped art supplies.
Let us not forget the fact that enchanting enough armor pieces and accessories with chameleon effects turns the wearer permanently invisible. Hilariously, people could see you fine in town... even if the player couldn't. These same people would not notice you if they then went outside the town gates and you stabbed them with a broadsword.
There's also the hilarious physics of jumping off items you're holding below you in mid-air, which makes for some great speedrunning tactics.
Oblivion has magic spells that spawn enchanted ("bound") armor and weapons. They have very strong attributes and zero weight, but the game balances this by making them only last for a while - then the spell wears off and they disappear. But if you let the item get damaged, repair it and then drop it, it won't vanish when the spell wears off. You could then pick it back up and have it permanently in your inventory.
If you attack a guard in the Arcane University, occasionally every NPC in the University will break out into a full-on brawl.
And then there is the famous door physics glitch. If you drag a body into a doorway and then shut the door in just the right way, the door will close and the body will get stuck in it. The collision detection goes crazy and results in a flailing corpse stuck in a door or wall.
If you are suspended from the Mages' Guild, you are required to gather alchemic ingredients for Raminus Polus to get back innote 20 Dragon's Tongues and 20 Redwort Flowers for theft, 20 Vampire Dusts and 20 Daedra Hearts for murder. If it's your first offense, a glitch allows you to get back in if you collect 20 pieces of only one of the required items.
Skyrim wasn't out for even a week before people found out that, due to how the new game engine handles eyesight, you could put buckets on people's heads and they won't see you stealing.
Realism at its finest. If they could figure out how to take off the buckets, it would be nice though.
According to Todd Howard, they learned about the bug the day after release. The lead programmer wanted to fix it but Howard insisted it be left in.
This being an Elder Scrolls game, horses being capable of climbing up ludicrously steep slopes is par for the course; but it is possible to get them to climb slopes that the developers didn't intend for them to be able to climb by holding forward onto a steep slope and waggling the control left and right; the horse will usually find some invisible purchase and glitch their way up the mountain. It is possible to reach The Throat of the World before learning the Clear Skies shout in this way.
This bug is inherent to the physics of the Gamebryo Engine (which Skyrim's engine is not at all based on) and has showed up (much less frequently) in previous games using it. Conditions that mimic the attack of a giant's club are just much rarer, but can be obtained by kicking downed bodies with weapons with lots of kickback (like the ballistic fist from Fallout: New Vegas).
This bug comes from the fact that the game's physics engine uses a momentum point system on a ratio to that damage of an attack. So when that giant hits you with its club (which is a one or two hit kill), it deals its damage to you and, should you die, it converts the extra damage to momentum points on your corpse (the more points the farther you fly) which is why you tend to just fall down if it's a late game one-hit kill but go flying if it's a late two or an early two (you can try this yourself by having a weapon capable of massive damage like a hammer with a high fortify strength and using it to hit a wounded opponent).
While the giant's club is specifically an item, it's also flagged so your character cannot pick it up and wield it. Your followers, however, do not have this restriction. Thus, it's sometimes possible to order your follower to pick up a club, meaning you get to see Lydia beating people with a massive bone bigger than she is.
Due to another physics bug, riding your horse onto the head of the dragon from above has... interesting effects.
Casting a fireball on a dead dragon skeleton will toss it around like a toy. If you do it on top of a mountain, it will fly further than the console's draw distance.
For some reason the Jagged Crown never counts as headgear and sometimes wants to count as a shirt.
Potions of Fortify Restoration increase the power of restoration spells and effects. This includes potions and (clothing/armor) enchantments. You can enchant equipment with Fortify Alchemy, which will also be effected by the potions, allowing you to make more powerful Fortify Restoration potions, boosting your Fortify Alchemy Enchantments(though you have to unequip them and put them back on after each potion for it to take effect); repeat ad infinitum. This eventually leading to potions and equipment that bestow billions of hit points, let you Shout without cooldown, or kill a dragon with your bare hands.
Completing the Daedra quest "Discerning the Transmundane" earns you the Daedric Artifact "Oghma Infinium", a tome that boosts all skills in one of three classes (Warrior, Mage or Thief) by five points. However, the downside to using said tome is it will disappear after first use. Before patch 1.9, this could be avoided by exploiting a glitch involving a bookshelf and careful hand coordination, allowing you to boost all skills over time and reach level 81 before even making it through 1/8 of the main quest. The patch which fixed this not only prevents you from doing the trick, but actually punishes you for attempting to try it—the book will disappear from the game completely if you attempt to put it on a bookshelf, preventing you from gaining the bonus you're supposed to get.
It's not particularly useful that sometimes mannequins animate and might walk and follow you around. But the scare it gives you sure is fun.
One of the biggest complaints about the 1.9 patch is that it removes a glitch that would occasionally cause the courier to show up wearing only a hat.
If you steal from someone, even if you aren't caught, eventually you will run into three goons labeled "hired thugs" sent to kill you. Kill them, and at least one will have a letter signed by the person you stole from, typically a home owner. However, a bug leads to just about anyone and anything capable of hiring thugs to kill you. This includes children, guards, animals, monsters, ghosts, and even people you haven't even met yet. Some will even send hired thugs after you for knocking things over and may send thugs after you even after they are dead.
In Final Fantasy, the creators accidentally had a four-square peninsula on the world map belong to the wrong monster area, making the enemies there be much more powerful than the ones normally fought at that point in the game. The "Peninsula of Power" was popular enough for power-leveling that it has stayed in the remakes, and inspired similar high-powered monster hideaways in subsequent Final Fantasy installments.
Also, in the PSP remake, with the glitch described here, one can turn low-level equips into top-tier equipment, as well as equipping items on classes that shouldn't be able to use them, such as the Barbarian Sword, the strongest weapon in the game equipped on the White Mage.
There is an item duplication bug in Final Fantasy III for the Nintendo DS. On the one hand, finding Phoenix Downs (which revive fallen characters) is extremely rare and there exists a limited amount of them in treasure chests, making each and every one a precious resource; on the other hand, being able to duplicate them at will can annihilate the game's natural difficulty.
Plus, rather early in the game (before the second dungeon or so), you find one elixir. What you are supposed to do with it is give it to a sick NPC in the town you find it in, and you get a rather impressive stash of treasure for giving it up. You won't find another for at least 3 dungeons, and even then, there are only 20 guaranteed in the game. It completely ruins any game difficulty, as that one elixir will last you for a long, long time.
The original Japanese version of Final Fantasy III has some wonderful glitches, like the item upgrade glitch that exploits an inventory stacking overflow error to alter the types of items, making it very easy to obtain most of the Onion equipment.
Final Fantasy IV allowed you to duplicate anything that could be equipped on the left or right hand through an equip glitch, even items that could only be obtained once in a regular play through. This was incredibly handy for dual-wield characters and gave Edge many more weapons to Dart (multiple copies of the Excalibur sword, for example). You could also sell the more valuable dupes for tons of GP, turn around and stock up on other items in shops, which was especially useful when trying to purchase high priced items like Ethers and Elixirs. It was also possible to equip a shield on Rosa and Rydia, substantially increasing their staying power. This prevents Rosa from using a bow and arrow, but the "Life" staff works fine. This only works with the SNES and PlayStation versions though, not the GBA port or DS remake.
The Crystal Room Warp Trick from Final Fantasy IV allowed the party to skip the Sealed Cave entirely. Unfortunately, it was removed from subsequent rereleases and remakes.
Relm Sketch Glitch: Using Relm's sketch command under certain conditions might erase your game... or it could max your hitpoints to 9999, fill your inventory with secret items and turn Edgar into the fallen hero Leo. While the glitch is potentially dangerous, the conditions to trigger a given result are also predictable enough to be safely exploited if you know what you're doing. The short version on why it works the way it does is more or less detailed in the intro paragraph of this trope, and later releases of the game fixed this glitch.
The evade stat never actually gets used for physical attacks, like it's supposed to. Instead, evasion to everything evadable in the game (which includes the vast majority of spells) is ruled by the m-block statistic, and it is possible to max out this stat, making the character Nigh Invulnerable. This has an interesting consequence for the game's "Dark" status, which blinds a character; it effectively raises the enemy's Evade when that character attacks; this has no effect whatsoever, due to the bug! There's also an item called "Goggles," whose only effect is to prevent the "Dark" status, so of course, the Goggles Do Nothing. This is fixed in the Game Boy Advance remake. The Dark status effect does have one negative effect: it prevents Strago from learning any Lore spells while he has it.
The Psycho Cyan glitch causes Cyan to launch physical attacks non-stop—not allowing anyone else to move—until all enemies are dead. It's a bit of a pain to set up, but is plenty entertaining if successful and a huge help to players attempting Low Level Runs. Here's a demonstration.
To explain what's going on: First you have Cyan use his second Swordtech/Bushido art, Retort. This puts him in a status where any normal attack on him will cause a counterattack against the enemy. Then, you turn him into an imp, which causes most of his techniques to become unusable — but does not take him out of Retort status. Then you kill him with a non-physical attack, such as a powerful spell or Doom. When he's dead, if he still wasn't attacked and did not act, he's still in Retort status, and now the computer isn't keeping track of what target needs to be hit to set off the effect. Then you revive him, and attack with anyone — or wait for the enemy to attack. Cyan will counter the mere fact that an attack was made, using a normal attack of his own (as he's an Imp), and will counter his own counters indefinitely. Well, until the enemy is dead, anyhow.
Vanish/Doom: Casting vanish on anything will remove its magic evasion (which is normal), but this means that instant death spells will always hit. Even against bosses that are normally immune.note This is because the coding that says "If target is under Clear status, and attack is magic-based, attack hits" takes priority over "If target is immune to instant death, and attack causes ID, attack misses"; the GBA version reversed that. The only monsters that can't be killed in two spells are the ones immune to Vanish (of which there are few, because Vanish is supposed to be a positive status ailment) and undead enemies (since Doom heals them; they're already dead after all). In the case of undead, though, you can just cast X-Zone instead; since it tosses them into another dimension rather than killing them, already being dead provides no protection. This only applies to instant death spells (and revival spells, which are usually not worth the effort), and fixed in the Game Boy Advance half-remake (though it still works on monsters NOT immune to instant death normally, this is expected and far less game-breaking).
The original Japanese version also included a glitch that let you equip absolutely anything as a helmet. The best helmet in the game? A drill.
And they knew it too(eventually)! It got referenced in Dissidia with the "Machine" armor set!
When Setzer suggests marriage to Celes as his win condition on the coin toss, Celes blushes. However, Edgar and Sabin share the same colour palette, and blush too. It's cute.
A couple of nifty Slot glitches: Strago can learn L5 Doom from 7-7-7 Joker Doom, and, by muddling and unmuddling Setzer, 7-7-Bar Joker Doom, ordinarily a Total Party Kill, can be reversed onto enemies (including ones which outright prevent a 7-7-7 Joker Doom, such as the very final boss).
The Rippler spell, one of Strago's possible Lores, allows the user to trade status effects with the target. Normally, one would assume this means the Standard Status Effects and Status Buffs; however, it also includes things such as Gau's Rage, Mog's Dance, and Shadow's dog. With some Rippler maneuvering, Interceptor can be set (permanently) to guard whatever character the player decides needs the protection, instead of guarding Shadow.
However, if an enemy uses Rippler on Shadow and the enemy dies, Interceptor goes with it and the dog is Lost Forever. Oops!
Sabin being able to suplex a train comes to mind. Sure, it's a once-per-game experience, but seeing him throw a locomotive into the air and slam it back on its rails is both awesomeandhilarious.
For even more hilarity, if you use Suplex but Sabin gets hit with Confusion before he can use the move, he can suplex himself.A video of this
Wind God Gau. Gau isn't supposed to be able to equip weapons, but in the original SNES version, he could equip the Merit Award, which allows any character to equip certain weapons and armor. In this case, give Gau one of Cyan's swords, the Kazekiri (Tempest), which randomly casts Wind Slash 50% of the time. Then give Gau the Master's Scroll (Offering) relic, which allows him to attack four times, and use the Stray Cat Rage and hope he uses Cat Scratch, which does quadruple damage. If you're lucky, Gau will attack four times at quadruple damage and use the Razor Wind after each strike. Later releases of the game remove Gau's ability to equip the Merit Award, but the technique could still be utilized by Gogo in the PlayStation port, until the Game Boy Advance port phased out the Wind God altogether by barring Gau and Gogo from using the Merit Award relic.
Final Fantasy VII had the W-Item materia. It allowed you to use two items in one turn, but due to a glitch also allowed you to create infinite copies of any item usable in battle. Including rare items, expensive items that could be sold to shops for loads of gil, items you're only ever supposed to get one of, and items that are Game Breakers in their own right when available in mass quantities. Done improperly, though, this can also result in losing items.
By endlessly copying Elixirs you can spam them on Magic Pots, which drop the most EXP and AP in the game, thus allowing you to break the game even further
Abusing this glitch greatly speeds up the chocobo breeding quest by replicating an otherwise very expensive item that is basically a chocobo steroid. Just for fun, stuffing the final gold chocobo (the offspring of similarly suped up birds) will give you a golden feathery god as far as racing goes.
Also; the "Quadra Magic Glitch", which lets you get the Quadra Magic materia without doing any chocobo breeding. See here.
Vincent's final weapon increases in power the more enemies Vincent kills, up to a cap. However, if you kill a ridiculous number of enemies (around 65535) with him, the damage formula for the weapon overflows, which triggers a failsafe script (possibly so that Vincent doesn't end up healing his enemies with the weapon, making it useless) that forces any target hit by the weapon to die instantly. Yes, even Emerald Weapon and Ruby Weapon.
The Turbo MP materia which increases both damage output and MP cost by up to 50%, also has a cap bug that prevents the MP cost for growing above 255, making it cheaper for anything that cost more than 170MP: Such as Knights of the Round Table, 250MP, which coupled with Turbo MP costs only 255MP instead of 375.
Not nearly as well known: Under normal circumstances, it's not possible to use the support materias HP Absorb, MP Absorb, Added Cut, or Steal As Well with either the Slash All or Double Cut command materias. It is however possible to put any of those four support materia in a pair of linked slots with Master Command; if you also have Slash All or Double Cut equipped, the benefits of the support materia will be added to them as well.
Want to heal your party to full-health in the middle of battle? Cast Regen on the party, then pop the lid on your Playstation open, then have someone in your party cast a magic spell. The whole battle will grind to a halt until you close the cover, but Regen heals your party in real-time, so you can wait out your injuries before resuming. Later entries in the series, such as Final Fantasy IX, prevented this by pausing the game if the cover is opened, but you could still use Regen and cast a summon spell with an impossibly long attack animation for a similar effect.
Red XIII's Howling Moon Limit Break boosts his attack power by 60% and also adds the Haste status to him. This sounds like an awesome ability, except that he also gains the Berserk status, which forces him to constantly attack, which can suck if you've equipped him with some good materia that you need him to use. If you give him a Ribbon or a Peace Ring, two accessories that block the Berserk status, Red will gain the attack bonus and the Haste status if you use Howling Moon, but you'll still be able to control him.
In Final Fantasy IX, adding Auto-Haste and Auto-Regen, and some other things, you can effectively have Auto-Regen fire off so fast, your characters can't die unless they've been hit with an attack that takes out more than their max HP.
Final Fantasy Mystic Quest: Clearing a battlefield with enough experience to gain a level will automatically increase your level again. Also, four words: Cure Kills Dark King.
To be fair, the levelling system means that for the next level along you need to get the experience required for the 'skipped' level along with it as well. Also, for people that were wondering why the spoiler qualifies, this is a case of cure working on something it's not supposed to work on (and indeed, only one of the party members' cure works this way).
The PS1 version of Final Fantasy Tactics had an awesome glitch that could let you get all the abilities of certain jobs. If you had enough JP to buy a skill, you could press down square, hit accept, then exit, which could make your JP for that job 9999 (though it didn't work for every job). This lead to fun things like Half-MP Bahamut in Dorter slums.
There was also an item duplication glitch. Putting a weapon in a character's left hand, and a shield in the right, and hitting optimize at the item shop would swap out the weapon, by putting the one you had back in your bag, and purchasing another from the shop. This could then be used to get infinite copies of one-time only weapons.
There was also the Samurai's reaction Blade Grasp that allowed characters to block not only swords, but arrows or even bullets. It works in the PSP version as well, and it's awesome. Catching bullets!
If you use a gun to jump on something with Blade Grasp equipped, you'll skywalk.
The first stage of the Deep Dungeon/Midlight's Deep occasionally spawns a male Time Mage... who isn't actually male. The Mage in question is female in every sense except her portrait and in-battle sprite. She can be Invited into the team (and remains a crossdresser should you try), even using Bard sprites for the female-only Dancer class. It could, in theory, be a very obscure Final Fantasy V reference, but more likely it's just a very funny and ultimately harmless bug.
Blitzball in Final Fantasy X has the AI of the computer-controlled players completely forget the player's existence if he swims to and stays by his team's goal. It's easy to win by scoring a goal, getting the ball the next turn, and swimming over to the goal, then waiting for the time to run out.
For some silly reason, the Cover ability works on the various worm monsters when they use Regurgitate to spit out a character they swallowed earlier. The result is the user teleporting into the worm's mouth and being spat out in place of the intended character, which causes the "protected" character to become invisible (Save for their weapon), but still usable, which serves no purpose other then looking ridiculous.
Although not really a bug, but equally silly looking, casting a summon causes dead characters on the field to get up and run away. When the summon finishes or dies, the characters run back onto the field and promptly pass out.
Thanks to some backwards math, the Saw item in Makai Toshi Saga is an instant kill against strong monsters, like the final boss, instead of weak monsters.
Plus martial arts weapons, which get stronger the fewer charges they have left, stack. List a near-empty Headbutt above a fully stocked one and the fully stocked one will do as much damage for each use!!
Sa Ga 2 fixed those bugs, but added a few more, most of it Robot-related (new class). Robots get stat bonuses for their equipment as long as they have it equipped. Wearing martial arts weapons gives Agility, but they don't deal the progressively higher damage per use. But once a Robot uses up said weapon, it disappears and they still keep the stat bonus.
SaGa Frontier has Takonomics, named in honor of the man who discovered it: in Koorong, the price of gold goes down as you sell ingots and back up as you buy, but this calculation is (erroneously) made before any actual physical inventory changes hand. You can therefore manipulate the gold market in the shop menu such that when you actually sell your gold, you get more money back. Then you travel to Nelson, where gold ingots are always sold at a fixed price, and repeat until you have all the money you'll ever need.
In addition, the well-loved Overdrive-Stasis trick, even though it seems like it may have been on purpose due to the moves descriptions("Temporarily gain infinite speed" and "freeze time in battle"), is actually a glitch- see Zaraktheus' last post here for an in-depth explanation.* It can be taken even further with the use of the Shadow Servant spell, which creates a shadow doppelganger that copies any spell or attack you use, effectively doubling the damage dealt in those eight turns.
this glitch has a similar effect if a snake oil item is used by the caster on himself in lieu of Stasis, without the side effect of being in stasis after Overdrive ends. This means that time Lord does not have to complete the Rune Quest in the four quests which he is recruitable, and could be the most useful character in the game.
The Junk Shop glitch, which allows you to get endless free stuff from the Junk Shop in Scrap: just attempt to sell a HyperionBazooka that you don't have and you get seven free items. Perfect for either kitting yourself out with Disc One Nukes or building up enough money to engage in Takonomics.
Hoo boy, Pokémon. With the absolutely insane amount of people playing the numerous games around the world, many of the glitches in certain generations are widely known and abused, most of them found in Red and Blue:
In all generations, critical hits ignore enhancements to the appropriate defensive stat. In Generation I, they also ignored penalties. So a critical hit from a Normal move did only 1 point of damage to a Rock type even after a few Screeches while a non-crit attack with the same move did significantly more.
The first generation was riddled with Good Bad Bugs, including but not limited to warping everywhere from the very first town, even past the Elite Four, getting every Pokémon you want including Mew (not random), leveling a Pokémon from Level 1 to Level 100 in one battle by EXP underflow, walking through walls, etc.
The Japanese versions of the first generation games (except Yellow) had glitches based around the 11th item of the game, and some Pokémon. Wanted to instantly level up to 100? You could do that. Wanted an exorbitant amount of items? Same deal. In fact, you could "create" Pokémon with this glitch and a combination of things to do. For example, how to create Mew: You need three Pokémon. First slot: "Mew"; second slot: a water Pokémon; third slot: any Pokémon. Go to Route 1, get into a wild Pokémon battle, press Select on your 11th item, switch to the Water Pokémon, escape. Press Select on the 11th item again. Find a wild Pokémon, press select on your 11th item, switch to your other Pokémon. You should now have a Mew!
One of the most popular glitches is the Cinnabar Coast glitch (which also works on Seafoam Island), where there's no data for what Pokémon you're supposed to encounter there, so it uses the same data as the last place you were where you could fight and catch Pokémon, including ones found at the Safari Zone. However, if instead you talked to the Old Man who teaches you how to catch a Weedle, your name would determine what Pokémon (at monstrously high levels) could be found there — including the fan-favorite glitch Pokémon MISSINGNO., which allowed the player to duplicate hard-to-find items such as Rare Candies (which you can feed to a Pokémon to immediately increase its level) and the Master Ball (can be used to automatically capture any Pokémon, but you only got one during the course of a normal game).
The reason this works is because the game stores MISSINGNO.'s Pokédex info on the same place as the data for how many of the sixth inventory item you have, so just catching a glimpse of MISSINGNO. would give you 128 of that item, and actually catching it would give you 255, giving you practically enough Master Balls to catch the entire Pokédex and still have an extra 104 balls to spare. This glitch was fixed in the Spanish versions of Pokémon Red and Blue, as it was apparently discovered before it was released in that language.
Another glitch allowed the user to randomly encounter any Pokémon in Red and Blue in the wild, making it catchable... including the Event-only Mew, not to mention all sorts of randomly generated glitch Pokémon, with equally random move names and types (what you encounter using the glitch isn't random, actually, it's based off your last battler's Special stat).
Another glitch that blurred the Game-Breaking Bug line was a save corruption glitch in Gen I. Normally, if the Game Boy was reset while saving, the save file got corrupted and the game rejected it, insisting the player start over (or just go back to their previous save in later generations, which make back-up saves). But if the game is saved before receiving the first Pokémon and reset at the right moment, the game saves the number of carried Pokémon as 255 instead of 0. Switch a couple of Pokémon and now the item count is 255 when the normal limit is 20 items. What's in the other 235 slots? Pretty much everything else in the game, like the player's coordinates, the current area, the rival's name, etc. Switching items can lead to some interesting gameplay effects, including an extremely short game. This has since then been taken even further with other TASes that abuse the bug to beat the game in slightly over a minute or essentially allow the player to rewrite the code on the fly with their innateRapid-Fire Typing.
In FireRed and LeafGreen, there is the Nugget Bridge on which you can beat five trainers and then get a Nugget, only for the guy giving the Nugget out to turn out to be a Team Rocket recruiter who will battle you when you turn him down. However, he gives you the Nugget before you battle him, so if you lose you get sent back to the Pokémon Center and the guy keeps acting as if you never talked to him, including giving you a Nugget, so you can keep losing and getting another Nugget each time. Contrary to popular belief, this glitch does not work in the original games, as you only have one chance to fight him, even if you lose.
A bug in the Yellow version can make Pikachu like the player a lot from the first hour of play (use a Potion on it over and over again; even if it doesn't restore health, it still makes Pikachu like you).
This one is more like a musical quirk than an actual bug, but if a Pokemon happens to evolve after defeating Champion Blue in the Indigo Plateau, the music just goes silent until Professor Oak congratulates the player instead of looping the victory theme, since the "evolution jingle" doesn't loop. 
The cloning glitch in Gold and Silver: You could get multiples of one-shot Pokémon by shutting off the power of one Game Boy during a trade with proper timing (because the link cables used in the first two games couldn't send and receive data at the same time); and whatever item they held was duplicated as well, if you needed more Master Balls to get the Legendary Beasts.
Another way to clone Pokémon in G/S is as such: go to your computer, pick the mons you want, put them on your team, and save your game, then put them in storage. Then save your game again. As soon as the saving message gets to the word "off" in "Please don't turn off the power" (ironic, no?), shut off your Game Boy. You will now have one of each Pokémon on your team, and one of each in the storage box, and they will have the same held items as well.
This glitch can be used to farm the starters, normally only available as part of a gone-forever three-way choice at the start of the game. Save just before you pick, choose a starter, go catch a common Pokémon, deposit the starter in your box, then do the almost-save glitch; you'll boot up at the starter choice with your previous pick in the box you selected (unfortunately, this does not save the information for those starters in your Pokédex).
Early copies of the Japanese versions of Diamond and Pearl (removed from later and international versions, and not in Platinum at all) had a glitch allowing you to Surf out of the door of the first Elite Four member and into the black void at the edge of the screen; the big quirk about this glitch is that, if performed correctly, it will lead you to the event-only Pokémon Darkrai and Shaymin. Performed incorrectly, however...
The Celebi egg trick is absolutely brilliant in every way. It's almost a pity that things like this are so rare if not nonexistent these days.
And then there's a new cloning glitch introduced in Pokémon Emerald that did the same thing, except with linked Battle Tower matches.
There's also two cloning variations in Generation IV; item (easy to perform, JP-exclusive) and actual Pokémon (hard to perform, requires Wi-Fi, not restricted otherwise). Seriously, I wouldn't be surprised if every generation has an item cloning glitch...
And this picture wouldn't be complete without the Toxic Leech Seed glitch: use both of said attacks on your opponent, and as Toxic's effect of doubling damage from poison effects increases, so will Leech Seed's damage, in other words, twice as much damage each turn AND restoring a lot of your own HP.
In another Pokémon related example - the Acid Rain glitch that blurs the line between Game-Breaking Bug and this trope - in short, if Pursuit KOs a withdrawn 'mon while any weather effect is in play, the game goes insane - all weather effects are turned on and Pokémon get harmed by their own abilities that aren't meant to do damage ("Pikachu was hurt by Static!", etc.) - in short, Hilarity Ensues; but if Castform or Cherrim are sent out, the game will make them keep switching between their various forms until the game is turned off.
This person exploited the Pokémon bugs to hell and back.
In the fourth generation, there is a glitch called Tweaking. The relies on the player cornering so fast that the game fails load the appropriate graphics of a new area, allowing the player to walk through a black void to any location in the game. It has potential to allow access to Event Legendaries.
Due to how the GTS works in the fourth generation games, one can use a program on their computers to "spoof" it and produce any Pokémon they want to receive, with any attacks, items, nature, etc. Guess Game Freak forgot to put a failsafe in...
And recently, someone made a new program that supports Black and White by taking advantage of the exact same oversight! Will GF ever learn?
In Pokémon Emerald, the part of its random number generator that creates wild Pokémon's stats never reseeds. Therefore, with great timing (hit the right 60th of a second), you can get a Pokémon with great stats (perfect stats can take hours, so it would be frustrating if you hit the wrong frame). It also works in the DS games, however you will have to set the DS's date and time, too, and to make it a little harder, many actions in HeartGold and SoulSilver can advance or skip a frame or two.
Another glitch with the GTS allows you to evolve trade-evolution Pokémon without actually trading them. Basically, put the Pokémon up for trade, but request an impossible Pokémon in return (like a Lv. 9 or under Mewtwo). While it's sitting there, engage in a trade in the GTS using another one of your Pokémon. Once that trade is done, retrieve the Pokémon you put up for trade, and it will evolve! You can combine this with Disk One Nuke to get the likes of Kingdra and Machamp as early as the THIRD Gym.
A bug in Pokémon Stadium 2 allows you to get infinite continues in any cup (but not Gym Leader Castle). Just have a suspended game, then start any cup (not from the suspended game), and make sure that you have at least one continue. After that, whenever you lose, choose "Suspend" then choose "Continue without Suspending". Et Voilŕ! No continues are lost. This is very useful because the game is heavily rigged towards the CPU, especially in Round 2. This bug doesn't work in the original Stadium because if you try this, the game would just take you back to the screen with the Continue/Suspend/Quit options. But the original Stadium is easier anyway if you use loads of Psychic-types.
There's a glitch in Pokémon Colosseum that allows you to use any variety of Poke Ball an infinite amount of times.
Wild ARMs 1 has an item inventory glitch where if you switched places of items during battle after having other characters use them, it reduced the number of the wrong item. How this works is that an empty inventory space is still marked as "containing" the item that once occupied it (at the beginning of the game all the empty spaces are marked as duplicators or something), so if you used an item marked as "0", it'd roll "back" to 255. If you decided to duplicate Apples, then your characters could become little walking gods almost literally a couple of hours into the game.
You can do the same thing in Wild ARMs XF by having 1 item, then having a Harpy steal it in battle and then using it at the same time.
The same glitch is accomplished in the SNES version of Final Fantasy V by combining the Steal and Throw commands with the 2-Handed ability and some inventory management. Furthermore, because the shops aren't programmed to handle quantities higher than 99, you can sell your newly stolen items one at a time and never run out, yielding infinite cash as well.
A similar bug occurred in Pokémon Colosseum, being the first game in the series where you could catch Pokémon in Double Battles. One could use their first Pokémon's turn to throw a Master Ball, and on the second turn, switch the positions of the Master Ball and another ball. The Master Ball would catch the Pokémon but stay in your inventory, so you could catch every single Pokémon in the game from that point on with the Master Ball. Naturally, this was fixed in Pokémon XD.
Baldur's Gate 2 has another example of integer underflow. By using a potion from inventory and then switching it with another item, the other item gets used instead. This can give you several billion valuable gems, essentially granting you unlimited money from the start of the game.
Many of the spells in Baldur's Gate 2 were broken, making mages godlike, even more so than they are supposed to be. For example:
'Mislead' would create an illusory image of the caster and turn the caster invisible. The invisibility would not be dispelled as long as the image lasted, so you could beat everyone to death with a stick at your leisure, with the enemies being none the wiser.
Spells cast through 'Project Image' were not removed from your spell pool, allowing you to cast all your spells twice, or as many times as you memorised the 'Project Image'. Also, any monsters summoned through this spell weren't subject to the limitations placed on summoning, so you could conjure an army of planetars and watch them beat even the hardest encounters for you.
'Simulacrum' created a duplicate of the caster, also duplicating any items they held in their quickslots.
'Simulacrum' and 'Project Image' also stacked, with a PI doppelgänger being able to cast Simulacrum and vice versa. Careful use of spell slots made it possible to rapidly amass a massive army of cloned mages.
Better still, one of the two was immune to the summoning limit of five creatures. Thus they could bring forth massive armies of insanely powerful creatures, without running over the limit.
The special wild mage spells 'Reckless Dweomer' and 'Chaos Shield' were all broken, making this class powerful beyond wildest dreams. Spells cast through Reckless Dweomer weren't subject to one spell in a round limit that mere mortal mages had to observe. Using the robe that reduced casting time you could easily get four or five spells off in the time it takes for the enemy mages to cast one. The Chaos Shield, though not supposed to stack with itself would nevertheless do that if cast through a spell sequencer, virtually guaranteeing that you would never get a harmful wild surge.
One of the Wild Surges could lead to the cap of five summoned allies being completely ignored, as an Area Effect on your Mordenkainen's Sword led to you being surrounded by seven or eight razor-edged death engines. (One Let's Player had this happen on an elemental summoning spell and ended up reloading the game because it happened in quite a small room, meaning he had no idea what was going on.)
The 'Talk and Fight' bug was another useful, though very situational, bug: Any non-hostile character whom you are currently talking to or have a character lined up to talk to will have their AI disabled and will not go hostile while the character ordered to talk to them is underway. This allows you order one character to engage an NPC in dialogue, while ordering the other members of your party to, well, engage the NPC in less courteous modes of communication (like, say, a sword to the shin). The NPC, still waiting to be talked to, will sit there and take it as long as the would-be talker is still en-route and for several seconds afterwardse. While it will not work on any enemy that requires a scripted event to die (such as the Big Bad and the most difficult Bonus Boss), it does wonders against the game's literal dragons who are not hostile towards you by default. AI mods were eventually released to kill this problem.
In the first Baldur's Gate, one can export and import characters, and in the tutorial area there's a simulated Party that has good items for the low level (plate mail, a + 1 shield, wand of heavens, etc). Normally, any attempt to loot and walk out is thwarted since "Those items are illusionary". Clever players figured out you can save in the party tutorial stage, export the character, and then import them into a new game, allowing them to have equipment they should not have at that point, or enough vendor junk to buy good items your character shouldn't be able to buy - making the game up until the Mines a breeze. Sadly, they made the tutorial items in Baldur's Gate 2 unusable if you tried the same trick.
Amulets & Armor has a great bug dealing with the "death cam", the red-tinted view of the world you see when you die. Your character is actually still alive, the game just disables the keyboard. However, A&A has mouse navigation too, which it doesn't disable, letting you explore (and even beat) levels while dead.
One of the skills that can be learned well into Lufia: The Ruins of Lore is Sacrifice, a free move that deals 999 damage to a non-boss enemy but kills the user... unless you target yourself, in which case Sacrifice is an awesome skill that fully heals yourself without cost.
There are also two easy ways to get huge sums of cash quickly. The first uses Blue Tea, an item found only in Ordens (limited time offer!) that can be bought in bulk for 100 each and then immediately sold back for 150. Later, when the blacksmith in the beginning area becomes available, a simple bug can be used to get a limitless amount of whatever item he just made (except the last), creating an even quicker supply of cash. Stock up on cash when you get the chance, and you can buy the very expensive and (at that point in the game) game-breaking Zircon equipment later.
Before Ruins of Lore, there was Lufia II: Rise of the Sinistrals. One of the Bonus Boss enemies, the Egg Dragon, had the highest amount of HP possible. However, the programmers failed to cap his HP, and beating him is a simple matter of healing him with the weakest potion to cause his HP to roll over to double digits and then attacking.
The other Bonus Boss, the Master Slime, is more of a case of Puzzle Boss disguised as a Good Bad Bug: you need to either kill him through pure damage or kill your own party to win the battle properly. However, neither option is easy, since you only have 3 turns to kill him and the first thing he does is heal your party to full, and if the 3 rounds pass without him dying, he attacks himself and kills himself instantly. Either way you can't really lose the battle per se, but not doing the above causes him to say that you've failed and he won't give you a key to a room with a bunch of Bragging Rights Rewards inside, forcing you to redo the entire Bonus Dungeon from the beginning for another attempt since it has no save points.
Although both have been fixed, Diablo 2 had a couple of fun ones for a while. The big one was the homing/pierce bug, which let Amazons with the Buriza-Do Kyanon unique crossbow and the Guided Arrow skill strike an enemy up to 4 times with one shot. The other one was the Marrowwalk glitch. Said item gives charges of Bone Prison at level 33 (when the skill level cap is 20 without items). If a Necromancer, who can learn the skill naturally, equipped the boots but had yet to put an actual point into the skill, the game used the 33 given by the boots for synergy purposes. That means over a 150% increase in synergy power compared to actually leveling the skill, which meant a lot considering how all the bone skills tend to synergize with each other.
The first Diablo had a cloning glitch: if you picked up an item off the ground at the exact same time as left-clicking a potion from your belt, the item would appear in your inventory and the potion would be replaced with the same item. Extremely useful for fast cash or online item trades, as rare items sold well, but you could also have duplicate rings (the only item that you were allowed to wear 2 of the same thing).
Could be easily abused to create a level 1 character with maxed stats, as well, as the game included elixirs that each permanently increased a primary stat.
A possible item affix determines if an item increases or decreases the light radius (and thus how far a player can see) around the player character. While the original intention of this stat is that a higher light radius is good and a lower light radius is bad (because stumbling around a darkened dungeon is not exactly the sanest thing to do) to the point that -lr items are considered cursed and a -lr modifier is considered the necessary drawback on several unique items to prevent them from being overpowered... This isn't exactly the case. Light radius is also responsible for determining just how far away monsters in the dungeon activate and begin hunting you down; a higher radius means that more mobs will be out for your blood and a lower radius means you can actually apply some stealth tactics.
In Earthbound, there is a bug concerning the use of the condiment items with any food item in the bottom two slots of a character's item-list during battle which can be exploited to use the random-stat-increasing "Rock Candy" item infinitely. Additionally, due to one condiment being able to double the increase effect of Rock Candy, this allows even HP-lacking characters like Paula and Jeff to easily exceed 1000 HP with about 30 minutes of abuse and a subsequent level-up. Earthbound's HP display is limited to three digits.
The strange way MOTHER 3 saves and loads data can cause an accidental New Game+ in which you begin with the best equipment and all PSI.
Tales of Symphonia had an interesting skill system where each skill basically had two different skill trees, but the skills from each tree were mutually exclusive. There was a glitch, however, that allowed characters to learn the highest-level skills from both trees at once, which was especially useful for the resident magic-user, Genis. Sadly, this glitch was fixed in the PS2 remake.
The game also included passive bonuses from a sort of item slot system, one of these bonuses was the "Randomizer" bonus, which would give a spell sometimes a chance to cast instantly, or make it take longer to cast. The player could easely abuse the fact that a spell can instantly be cancelled and then be recast as well without any lag to throw the strongest spells at anything with pretty much instant cast times.
Tales of the Abyss had an interesting glitch that allows you to play as Asch longer than you're supposed to. From time to time, you switch from the Designated Hero Luke to the Anti-Hero Asch. During a sidequest in mushroom forest, if the player ejects the DVD but keeps the game running and have Asch exit the other way, he'll be able to exit the forest, go through mountains, go to a city, save the game, and continue with the main story, as Asch. There are no side effects in doing this aside from a few weird moments since the lines that are supposed to do with Luke is switched, so the player can complete as Asch. It is sort of advantageous, since Asch, unlike Luke, is a Magic Knight, though later on, his usefulness decreases.
Finishing the game while playing as Asch will make it so, when you start the New Game+, you won't have Luke on your party, so the game will always freeze on the tutorial battle, as you won't have any character in your party. Turns into a Game-Breaking Bug if you saved the finished game data on the same slot, as you're now trapped forever before the tutorial.
It also has other numerous bugs that weren't fixed during the lengthy american localization, but still many of them are benign or require the player to do something like open the Disc Door on the world map or repeatedly equip, unequip, then re-equip a title to buy and sell stuff - Whoever discovered those must have had a lot of time on their hands. One such bug is opening the Disc Door while on the world map. It enables you to travel anywhere on the world map and you can even pick up hidden items that you would have missed past the Point of No Return. Another bug would be sealing the hidden boss Nebilim's mystic artes so she can't use her deadliest attacks on you.
In Fable, the shopkeepers semi-realistically changed the prices of their items depending on how many they had on them. A jeweler who sells wedding rings will charge far more for his last one than he will for the first of 500, and if you happen to have an extra one to sell to him, he'll pay way more if he's out of stock than if he has them piling up in storage. By the way, there are "Buy All" and "Sell All" commands. Buy All for cheap, Sell All for twice what you paid half a second ago... easy money. Too easy. As buying and selling earns you experience in your Skill exp pool, spending an hour or so abusing this not only gives you near-limitless cash, but also makes you into the ultimate archer.
Knights of the Old Republic and its sequel are packed full of these, from infinite money and experience exploits to infinitely powered up lightsabers to item duplication to leveling up any follower as a Jedi.
There is one SINGLE conversation choice near the end of the game that will drag the player character's morality bar from either extreme right into the neutral zone if their response is contrary to their behaviour thus far, and will set the ending received irrespective of prior behaviour. However, if all other choices in said conversation and following it follow the ORIGINAL behaviour and run contrary to that single choice, it is quite possible to slip back into the previous morality and get the Light Side ending with a Dark Side character (including the special morality-specific robe options) and vice versa.
During a duel to the death in the original KOTOR, it is possible to stop combat just to ask your enemy if you can have his autograph. This happens if you challenge Bendak Starkiller to a duel but don't ask him for an autograph beforehand. In the opening seconds of the duel you click on him to attack, but the game makes you run up to him and starts the dialogue sequence that stops him from attacking you. This bug can be used to get close to Bendak before he has chance to shoot at you and thus avoid damage that you would suffer if you ran up to him.
If the player starts out as a Scoundrel, then becomes a Jedi Guardian, it is possible to combine the Force Jump and Sneak Attack abilities, causing the player to leap across the map and deal a massive amount of damage to whatever they hit.
In the second game, the Handmaiden duels are just plain glitchy:
One glitch involves cheating at the Handmaiden's training game and then berating her for calling you out on it. Like the Hanharr glitch, this is only supposed to happen once or twice, but it can be done over and over for infinite dark-side points and influence with the Handmaiden if you do it right.
It is also possible to get unlimited copies of her sparring robes by agreeing to fight her with them on, then tell her you're not ready yet, unequip them and start over from the top. The robes are worth a mint. Do the math.
By switching weapons during one of the Handmaiden sparring matches, right before she becomes "hostile," it literally turns it into a Duel to the Death. That's right. You can kill the Handmaiden on the Ebon Hawk. If you exit the ship, she will not be available for your party. If you re-enter, however, she will be back.
In the second game, if you choose to fight in the Mandalorian battle circle, breaking the rules of the duel (such as bringing a lightsaber or Force powers to a fistfight) counts as forfeiting. However, the developers forgot to check if the player had planted mines in the dueling area beforehand...
Gothic has the Infinite Meat Bug, where sometimes the act of cooking a piece of raw meat will create a piece of cooked meat without eliminating the raw one - effectively duplicating it. As the player's inventory is infinite, and the meat can then be sold to traders or eaten to restore HP, this is fairly useful.
This worked for forging swords too. Lots of Ore (in-game currency) ensues.
Gothic 1 also has a bug where if you strafe while falling you will not take fall damage upon impact. Good for getting around faster and getting to areas normally inaccessible.
No doubt the most game-breaking bug of all is the Exponential Item Multiplication bug, which occurs in the unpatched game when you try to put an item back into the inventory of an unconscious (but not dead) human enemy. Due to a typo in the code responsible for this section, any item stack will increase exponentially whenever you add another item of its kind to the mule's inventory. This means that if you have at least two of any particular kind of item, you might as well have infinite amounts.
Gothic 2: The Night of the Raven had mage staves that increased your magic points when equiped. Problem is, they did it permamently.
In Gothic 2: The Night of the Raven there is a method to obtain very powerful runes for a mage without looking for rare ingredients (which is tedious) or praying to the Beliar (which costs you health points). All you have to do is to kill a Seeker in a very specific way. First, bring them to the verge of death by reducing their health points, then finish them off with an Ice Block spell. Now, when a Seeker thanks to the spell is still standing frozen solid, but in fact he's dead you have a few second to search their corpse. If you're lucky, you can get strong runes such as Rain of Fire or Cry of the Dead. Note the fact that this is the only way (aside from using codes, of course) to steal a rune from the Seekers. If you kill them in a normal way, runes will magically disappear from their inventory.
Phantasy Star Universe 's first summer event introduced swimsuits. These were treated as a single item that takes up all three clothing slots, meaning you couldn't mix-and-match as you can with the rest of the game's clothes. By going into the Xbox 360's Guide and choosing "Join Session in Progress" with another friend playing the game, all your clothes would show up as unequipped, but you would still be visibly wearing them, allowing you to equip another "layer" of clothing over the first. By having a swimsuit as your first layer, you could then put on some normal pants, while keeping the swimsuit top (bikini top for girls, shirtless for guys). Though the bug was fixed, it was popular enough the swimsuit items were later split into separate pieces for the tops, bottoms, and sandals.
In the Playstation version of Azure Dreams, careful use of a certain transforming Mon can allow the player to duplicate items as long as their monster has enough MP to morph (intentional). Less careful use of the same monster can allow the player to freeze the game (unintentional).
Getting the surgical armor upgrades in Fallout 2 is costly since it takes one combat armor and several thousand chips each, and you want at least two (more if you can survive the Charisma drop). This could be averted with some doctors (Johnson in Redding for one) by agreeing on an operation, moving the conversation to just before it's about to start... then opening the barter screen and use the "drop item" function on your money and combat armor. You'd still get the upgrade, and can use your stuff for the other upgrades too.
The most widely abused bug in Fallout 2 gives the status effect of a drug used by/on an NPC to every NPC in that category (e.g. Slavers) on the map. This is a real Game Breaker, since players can drop the Perception of every enemy to 1 with 9 cheap bottles of beer, their strength down by 3 by giving one enemy Buffout and waiting 6 hours for the hangover, diminishing their Action Points by addicting them to Jet... Drugs Are Bad.
Some players use this bug as a Self-Imposed Challenge. That is to say, they only use the beneficial drugs without waiting for the hangover to make combat extremely difficult. Adding one or two Buffouts and Mentats and two hits of Jet results in fast and hard-hitting enemies for several dozen turns.
Fallout 3 has a bug in a quest where you must rescue a Brotherhood Initiate. Upon doing so, however, Paladin Hoss (who you must get the Initiate to) will start appearing next to you when you fast travel, then run away as fast as he can. But even better, sometimes he will enter your house and steal one of your guns (anything in the locker, or anything just left lying out). Then he walks out calmly, and if you kill him, you lose Karma. Luckily, the patrol he does round the Wasteland takes him near some cars with live reactors, just right for exploding. Then you can get back your gun from his body parts.
Hoss has been known to stalk players all over the wasteland, including DLC locations such as a hostile Enclave base, Point Lookout, and an alien mothership hovering many miles above the Earth's surface, materializing in full armour and toting a nuke catapult he stole from your house.
It is also sometimes possible to half-clip into objects, which will also hide you from enemies unless you move or they come in contact with your character. They won't, however, attack. There are some other areas where melee wielding enemies (most likely animals) will not attack you if you are standing above them, even though it would be entire possible for them to climb up a very gradual slope to kill you.
Another very useful exploit is the fact you can carry objects in your arms (well, floating in the air) that cannot be put in your inventory. While that would normally be useless, you can carry enemies. While that would still be useless (because enemy corpses encumber all but the strongest of characters with no gear), you can also simply carry an enemy's head (or other blown-off body part). You can then access the corpse for the items later. This led to a hilarious scene where, after killing a huge number of enemies, you stuff multiple chain lasers, rifles, foodstuffs, and essentially everything you could find in the wasteland into a raider's head, carrying it around everywhere as a second inventory. It's the modern bag of holding.
The game also has just plain wonky physics bugs. Sometimes if you approach the Deathclaw Sanctuary, you are treated to the sight of the mutated superpredators streaking up into the sky like rockets, never to return. Other times, jostled objects ricochet around at Mach speed, causing you to take damage from a flying femur. And occasionally corpses just fall out of the sky at your feet when you exit the building. Of course, such bugs become less fun when a quest object spawns but gets launched over the horizon before you can interact with it...
One good/bad bug added with the Point Lookout expansion is called the "Haley's Hardware Glitch". Each time you visit Haley's Hardware after visiting another area, his repair skill goes up by 5 points. You can milk this til it reaches the max of 100, which is very useful when it comes to rare items like the Alien Blaster, which has few options for being repaired 100%.
The infamous Gary 23 exploit. Using the dead body of a Gary clone, it is in fact possible to take items into the real world from out of a computer simulation. The glitch is lucrative due to the fact that the weapons inside the simulation have special scripts attached to them, giving them infinite damage resistance and rendering them virtually indestructible. Then there are other bugs, such as an exploit that enables a player to harvest unlimited amounts of ammunition from ammo dispensers. And then there's another well known bug that allows a player to zoom to level 30 by killing endlessly re-spawning friendly Chinese soldiers. All of these bugs combined can result in a major Game Breaker (or not, depending on whether or not you like fantastic bugs).
Related to Operation Anchorage is the Chinese Stealth Suit that you get by completing the mission. When wearing the suit, you can put on as much headgear as you want, which can seriously boost your stats (assuming you're wearing stat-changing headgear, of course).
Also related to Operation Anchorage, the Winterized T-51b Power Armor you receive after completing the simulation is a glitched version of what the devs had intended you to get. However, you won't mind, since instead of the 1,000 HP the armor was supposed to have, it instead has nearly ten million HP. The helmet adds another million. This is easily the best armor in the game, as it never, ever breaks down or needs repair.
One of the more interesting glitches involves escaping the room in the stat choosing scene as a baby. If you get past your father and outside, you can get into the vault 18 years later, as a baby. You can't actually do anything until you get to Megaton, but at that point, you can start attacking. You can go throughout the game world a foot tall, making baby noises every time you press a. You also move slowly, can't jump high, and can't see your Pipboy, because your face clips through it.
In the Broken Steel DLC, you get a device which will set hostile Enclave-controlled Deathclaws friendly, and will follow you around. However, it may disappear or de-spawn. There is a chance it will later spawn when you when you enter a friendly environment like the Rivet City Market or the Citadel. The Deathclaw is friendly to you, but not anyone else. Hilarity--and carnage--ensue.
If you shoot the Aqua-Cura salesman outside Underworld before completing "The Amazing Aqua-Cura!", he and the crowd will turn hostile. But if Fawkes is there and not a companion, shoot the salesman with a dart gun while hidden. Fawkes will go berserk, slaughtering the crowd and the salesman.
Another bug from Point Lookout involves the Ghoul Ecology perk. The perk is supposed to increase your damage against ghouls by five points per shot, but because the "ghouls" target is misplaced, it provides its damage bonus against everything.
SaGa Frontier has a bug involving selling gold nuggets called "Takonomics" in honor of the man who discovered it: the price of gold goes down each time you sell it (and back up each time you buy), but it does so before any physical inventory passes hands; thus if you "sell" your entire inventory, and then go back up to your original amount, the price of gold will increase by a dramatic amount so that you make a killing when you sell them for real.
Let us not forget the infamous "Junk Shop Glitch". Simply put, go to the shop in Scrap, which normally sells junk (hence the name Junk Shop) and works by letting you buy 3 items at various prices (depending on the main character's current strength). Normally the game only lets you pick out the three items, but if you go back to the shopkeeper and attempt to sell the last item in the list of stuff they buy from you (even if you don't have any), you can go back into the junk room and pick out 7 more items. You can do this infinitely. Better yet, the quality of the items you can get will actually increase as you sell RepairKits, which is conveniently one of the items you can find at the shop (unless you're T260G), meaning you can potentially have some of the best gear in the game (like LethalGuns and ExcelShields) less than an hour into it.
The well-loved "Overdrive/Stasis trick is a glitch as well, despite the way the skills work making it seem intentional. By using Stasis as the last move of Overdrive, the character can have up to 8 turns for the duration of the fight. It can also be performed by either using a Snake Oil or casting "Grail" at any point during the Overdrive, which is part of what outed it as a glitch.
Since Artix Entertainment is always working on a once-a-week deadline for four different games, they tend to have a lot of bugs, and thanks to the law of averages, some of them work out to be awesome. In AdventureQuest, for example, it was briefly possible to deal billions of Hit Points worth of damage to one boss, and the first release of the necromancer armor in DragonFable had a "Final Strike" ability dealing two or three times what was intended.
Another bug for Adventure Quest was a result of an odd bug in a weapon called Power Katana. In Adventure Quest, the armor you are wearing determines the number of hits you do each time you attack, but it also determines how many percent of your weapons damage you do with each hit. The Power Katana, probably due to it being the only item that scaled with your level at that time, did not play nice with the latter, instead, each hit did standard damage, which was insanely broken if you paired it with an armor that preformed several weak hits, allowing you to do up to six or seven times standard damage. The bug was, however, fixed quite a long time ago.
Suikoden II had a bug during the first portions of the game where you could push a seemingly sturdy locked gate and complete a side quest you weren't supposed to many dozens of hours into the game later. If you can survive at least until you get to a town to recruit two party members to complete the side quest, you can level grind for a while. By the time you're done, you should have at least five characters who can kick ass and take names until That One Boss.
Speaking of Suikoden 2, there were some NPCs in the game who spoke gibberish when you talked to them. The translators actually forgot to translate some of the text strings from Japanese to English, and the English version of the game lacked a Japanese font, thus producing something completely illegible in either language.
And speaking of That One Boss, Luca Blight, there is a glitch that makes him incredibly easy, so long as you don't mind the fight lasting a lot longer and only the main character getting any EXP from it. Right before you form your three teams for taking him on, leave the room and form a team and place the main character in the back row. Then go to form your teams. He will be by himself again. Don't put anyone else in that group. When you reach the third battle against Luca, the main character will in the back row. All of his main attacks will completely miss you, and the only thing you need to worry about as you cherry tap your way to victory is an occasional counterattack. Even then, however, it does a negligible amount of damage that can easily be negated with a Medicine or two.
If you choose Stay at an inn and cancel out of the Don't Save/Save option, you will be fully healed without paying anything.
There is a trick in the Game Boy Advance version of Kingdom Hearts: Chain of Memories that allowed Riku in dark mode to keep the effects of support cards that affected a finite number of attacks like Overdrive and Attack bracer indefinitely. All you had to do was double-jump and attack. You deliver a multi-hit attack with the effects of the support cards and the counter does not go down. Useful for beating Ansem!
The Quest For Glory I VGA remake has a bug in which you could sell your mushrooms to the healer infinitely, even when she says she has enough of them, thus allowing one to rack up as much as 100 gold early in the game.
Quest For Glory V has a couple of bugs: The first is an item duplication bug, where you stand in an area and remove a single item in your inventory. The character, for some reason, throws the item up in the air. While it's still in the air, it's also still in your inventory—which means you can remove it again and watch the second inventory item sail through the air. If you're really quick, you can use this to duplicate a number of them before the first hits the ground. You can then sell the duplicates to the shopkeeper. Naturally this is best done with the expensive items in the game, like magic chainmail. It only works with a single item, though; if you have multiples of the same item, you'll just remove those multiples from your inventory. I believe it also only works with items that can be bought and sold to the centaur shopkeeper. The second bug occurs after the player completes the game once. After starting a new game, the PC can walk out of Silmaria and find the hot-air balloon already made and waiting for him.
The Apple II version of Wizardry had a bug where successfully identifying the "item" in slot #9 (you could only carry 8 items) would give your character 100 million experience points. This became an Ascended Glitch when it was intentionally included in the IBM PC version.
In the DS RPG Nostalgia, the Golden Chalice item revives a party member with full HP. Due to a glitch, using this item will also give the party member up to eight extra turns. With judicious buffing and multi-attack skills, it's possible to do Over Nine Thousand points of damage.
Dragon Age: Origins has two distinct bugs, both of which hinge on the fact that there are a few menu interactions where you can do the same action in two different ways. In the first case (infinite gold and duplicate items) you can double-sell an item by clicking the 'sell all' button, and the 'sell' button at almost the same time. Similarly if you have enough talent/spell points you can buy a low-level power, and cancel it while buying the higher level one at the same time, leaving you with the higher level power, and the extra point you sold back. Also, when adding stat point, if you press reset after adding stat points into it you can actually reduce the stat point by that amount (by pressing the reduce button after resetting), and thus gaining those stat points to distribue freely. Fear the Arcane Warrior with 0 strength!
At one point, you're traveling through the Fade, and obtain the ability to shapeshift into a few different forms with different powers. Once you leave the Fade, your shapeshifting abilities are lost, and you can't fool the game by assigning your various forms to the quickbar... unless you assign each form to the quickbar more than once, in which case you can turn into a golem or an undead sorcerer whenever you like just by clicking the icon. This has since been patched, alas.
Another Fade exploit comes from the various fonts and essences, each of which permanently increases one of your attributes by 1 when used. Rapid-fire clicking, however, can get you additional stat boosts, ranging from two or three points to double digits, depending on the font. The slower your computer, the more effective the exploit becomes.
In Dragon Age II, you can infinitely increase your armor stat by repeatedly un-equipping and re-equipping a shield. Any shield.
The infinite gold bug is back in DAII, and it joins a new one: if you turn in a Fetch Quest at the same time you sheath your weapon (you have to draw and then wait for Hawke to put it away), you can get the quest reward repeatedly every time you press the interact button. Do this for an arbitrary amount of experience and money and then buy the Disc One Nukes from Bonny Lem and the Black Emporium to make you a killing machine.
Again in Dragon Age II, it's possible to gain infinite talent points, due to some bugs that give player character some talents back for free after they reset their character, save, and reload. Continue resetting your character and you can have enough talent points to max nearly every talents you have.
In Dragon Age II's final boss fight, the boss will repeatedly paralyze all combatants in order to monologue... but if you've invested into Aveline's defensive skills, and have her in your active party, she'll be immune, and proceed to smack around said boss. It's as if someone asked: "Why don't you just hit em?"
You can be hit by a practice dummy during the tutorial. In order to use it as a target, they had to program it in as a creature; while it doesn't get normal attacks, it does get attacks of opportunity when you make a dim move near it.
Some weird combination of Rogue/Sorcerer, Charisma enhancing magic items, and a scroll of Tenser's Transformation can result in the player suddenly being able to cast each spell level they have 1024 times. You can go from having two Stoneskin spells to having more than a thousand, which in turn means you can handle physical damage equivalent to being repeatedly trodden on by Godzilla, with only a brief interval when you hide from it and cast Stoneskin again. As it happens, this also applies to elemental damage resistance spells. This bug was discovered when taking on a White Dragon. Cue large amounts of not dying.
In its early days, Kingdom of Loathing had a couple of these, which often looped from bad to good and back to bad again.
First were a couple exploits that allowed players to submit invalid item IDs in certain places, which would allow them to replace an item they were about to acquire with any other item in the game. This led to the creation of items like the "steaming evil" and "Item #13".
An infamous one was the Meat Vortex bug. The Meat Vortex item is a combat item, but using it from your inventory simply caused it to take away some of your Meat (the in-game currency). However, using it when you had little to no Meat on hand would cause an integer underflow, so -1 Meat would roll around to the former Cap of 18,446,744,073,709,551,615 (or 2^64 - 1) Meat, and any further losses would be deducted from that number. This caused massive amounts of hyperinflation in the game, and the cap was reduced to 4,294,967,296 (2^32 - 1).
There are two kinds of bug in Kingdom of Loathing: the "this was a programming glitch that shouldn't have happened" bug like the Meat Vortex glitch, and the "this isn't technically a glitch, but you weren't supposed to be able to do this" kind. Finding the second kind can be quite fun, because the dev team's reaction to such bugs is to give a trophy or some other kind of reward to the player that found it, then fix the bug.
In Mass Effect 1, there is a glitch on the planet of Noveria when you speak with the turian named Lorik Qui'in. You do the mission he tasks you with, then speak with Gianna Parasini before reporting back to him. If you have enough Charm/Intimidate skill points, you can use either option to persuade him to testify against his boss. The glitch starts if you immediately talk to him again and ask him about Matriarch Benezia. Afterwards, you get the same options to convince him to testify again. Depending on whether you use Charm or Intimidate, you get Paragon or Renegade points every time you speak with him. You can fill up one or both bars in minutes.
On a number of the open-world planets, you can shoot at enemies (generally with a sniper rifle) at such a distance, that their name and health won't appear on your HUD. They might fire back at you, but they'll never be able to hit you, and will just stand still. Armatures and Colossi may still be able to hit you with their large pulse missles, but all you need to do is find a hill or something else to duck behind while the missles runs into where you just were while you're safe. You can kill entire groups with this method, which may be boring, but is a godsend on Insanity.
In the "Lost Module" side quest, there is a space monkey you have to search to find the module in question. If you do so without shooting any of the monkeys, you get some Paragon points. But, if you save and reload the game immediately after acquiring the module, you can search the monkey again unlimited number of times and get paragon points every time. This is even easier to exploit than the Lorik Qui'in glitch, as you don't need any Charm skill, and you can just tap the button and fill your Paragon meter in seconds.
There used to be a bug in the 360 version of Mass Effect 2 which allowed you to essentially get infinite skill points, for both you and all 12 of your party members, if you didn't enable auto-level. By pressing A ("Buy Rank") and X ("Reset Talent Points") at the same time when buying a Rank 4 skill, you'd get the skill...as well as every point you spent on that screen. If you had at least 10 unspent skill points going in, then you could completely level up every single character in the game in one fell swoop. At level 6. Disc One Nukeindeed. This one was eventually fixed in a patch.
Hey, remember Conrad Verner? The creepy guy in ME1 who asks you to be a Spectre? You got the Paragon resolution to his sidequest, calmly explaining to him that he should go back home to his wife...but wait! There he is in ME2, wearing a full suit of your armor and harassing a bartender. He says he learned how to be "truly extreme" from you "shoving a gun in [his] face"...wait, what? That's the result of a save import bug, of all things. It always assumes you did the Renegade solution to his sidequest and adjusts the game accordingly (Paragon Shepard is supposed to get a different dialogue)...which actually makes the Paragon resolution funnier, because it turns ME2 Conrad from "This Loser Is You" to "This Cloudcuckoolander Is You".
Becomes an Ascended Glitch in Mass Effect 3, where Conrad will apologize for accusing you of pointing a gun at him, saying he was under a lot of stress at the time.
During the final fight at Horizon in the sequel, the Scions will not start attacking you until you enter the final area, but they can still be seen from the edges of the passage... Meaning the player can use a sniper rifle to take them out. Considering that this is one of the toughest battles in the game on Insanity, this is very helpful to a lot of people.
In the Arrival DLC, there is an intermittent bug that can cause some of the enemies to begin screaming "Waughhhh-aghhhhh!!" at you nonstop. It plays rather nicely into the whole indoctrination aspect of the DLC. In another instance, because Shepard's battle lines are carried over from the main game, s/he often has a tendency to yell "They've seen us!", even though the character is supposed to be on a solo mission. The bug is possible, although less common, in other parts of the game.
In this clip, a bug causes the game to act as though Kaidan is not present toward the end of the first game, resulting in Tali arguing with herself over whether to save the Council.
In some scenes in ME3 when a character tries to turn their head to face someone when speaking to them, but the character is behind them, rather than the character model turning, the entire head and neck will twist around 180 degrees. Usually this just happens during non-cutscene dialogue, but a conspicuous example is after Priority: Geth Dreadnought where Gerrel's head will twist around in an otherwise dramatic, high-tension scene.
Mass Effect 3's multiplayer mode (at least on PC) has an occasional bug where you glitch and suddenly you can move at super speed! Even faster walking speed than the fastest class and race selectable, making retrieval missions an absolute BREEZE if you get that particular glitch.
In the third game's multiplayer when you're carrying a retrieval objective you're normally not allowed to run, dodge, cloak, or use Charge, otherwise you drop the object; but some players have figured out that if you mash spacebar fast enough it's possible to sprint while repeatedly picking up and dropping the objective.
In Mass Effect 2, players discovered that, when reloading a gun, its ammo count changed at a specific point in the reloading animation, not at the end. By performing another action that overrode the animation at the right moment, it was possible to cut the process short while still reloading the player's gun. This created an ad-hoc timing minigame when reloading long-cycle guns like sniper rifles and most shotguns that could dramatically increase performance if done well. This became an Ascended Glitch, mentioned by Bioware forum posters and preserved in Mass Effect 3.
Not as epic as some of the above, but rather satisfying: in the old Action RPGAncient Evil, undead enemies, when slain, would get up again after about ten seconds. The tougher undead could permanently drain your EXP if they hit with an attack, so the best response was to run like hell. However, if the game was saved and loaded, any bodies on the ground would be converted into bones, and this included the bodies of undead. Bring one down once, save and load, and it's gone forever, probably to your relief.
The PSP version of Disgaea: Hour of Darkness has several bugged items that were not present in the PS2 original. A pair of glasses known as Foresight, which is readily available in the shop once certain conditions are met, contains specialists that are far more powerful than those available on any other item in the game, including maxed-out Statisticians and Armsmasters (which increase the rate of XP gain and weapon skill gain respectively) which come pre-subdued and can be moved to any other item immediately. In a game that literally requires hundreds of hours of grinding to get to some of the highest-level content, this can speed things up dramatically.
On the minus side, equipping one of these items will render a character unable to move, although equipping a second one will nullify this effect.
Oh, and if you enter the Item World for one of these items, every enemy will be a Laharl clone.
A level 1500+ Laharl clone.
Speaking of Disgaea, the fourth game has a cloning glitch. It's already helpful on its own to duplicate rare or unique pieces of equipment, but the fact that specialists are clones alongside the item pushes it into Game Breaker territory. Even common specialists can be cloned, maxed out, and stacked together quickly with this glitch, leading to absurdly powerful weapons and huge stat increases, as well as huge Exp and Mana bonuses, provided you have the right specialists. In fact, it is so game-breaking that Nippon Ichi fixed it with a patch (Said patch can be deleted if you have already installed it, but you'll have to delete all your saves along with it).
Since at least Disgaea 3 (both on the PS3 and PS Vita versions) and possibly earlier, any enemy that just so happens to be Level 99 accidentally has its experience calculated improperly and winds up having the Experience Points of an enemy that's Level 297 or so, which can be rapidly exploited (in Disgaea 3's case, by combining three Level 33 zombies during a certain level in Chapter 5) by getting your characters dozens of levels within an hour or two, allowing you to breeze through the main quest - assuming, of course, you manage to be able to kill them. It's potentially verging on Ascended Glitch now since this bug, while not explicitly acknowledged by Nippon Ichi, is still alive and well in the latest game in the series, Disgaea Dimension 2, where it can be done by simply using the Cheat Shop to turn the Nekomatas in Stage 6-1 to Level 99 by setting Stronger Enemies to Level 9.
In Dragon Quest IX, due to a memory bug that pops up in their semi-Randomly Generated Levels of a certain size or larger, it's possible to get floors with no monsters at all... or monster parties that all include a certain monster type. If it's one of those that drops the most gold in the game or their second-to-the-best Metal Slime, it makes the going MUCH easier than the developers intended.
Divine Divinity has the "Polymorph" spell that turns an enemy into a harmless critter. The duration for the spell should be only a few seconds... but it's actually permanent. And it works on bosses. And you get full exp and item drops. The game also has a movable bed in one house; most beds are unmovable, but this one was different because it was blocking a hatch. However unmovable objects have no established weight, and the game has no encumbrance limit. You could put the bed into your inventory and have a free health/magic restore whenever you wanted. This also works with combining two hay balls inside your inventory. And one more, you could multiplate identical items like gems by ofering them to a trader, then write a negative number into the "Place on table" option and enjoy 255 items sold plus one more in your inventory. For more awesome, traders like you much more for your generosity as well.
Fallout: New Vegas has several hilarious glitches that flirt with game-crippling status. Chief among these is the "Doc Mitchell" glitch - upon waking up in Goodsprings, players can sometimes find themselves opening their eyes and sitting up as Mitchell's head spins around 360 degrees as he talks to you.
Ordering the game from Gamestop and using the exclusive preorder code for the Weathered 10mm Pistol, then equipping it with a laser sight would lead to the player running around with a giant exclamation point on him or her. Evidently, this was caused by the model of the gun with the sight attached not being programmed into the game, and the exclamation mark is a placeholder asset.
Boone's ridiculous accuracy and ability to kill anything is the result of a game bug that occurs almost all the time, even to players who don't know about it. Because of a scripting error, Boone receives a perception bonus every time he equips a suit of armor or clothing. The only problem is that these bonuses stack infinitely, allowing him to obtain a 100%-plus hit ratio.
In a bit of pure irony, a glitch can be used to workaround a different glitch. Vault 22 has a glitch where if you use the elevator, your companions will appear next to you, even if told to wait elsewhere. This is useful since certain companions have a tendency to disappear for pretty much no reason. You can exploit the Vault 22 elevator to recover those companions.
Collect some Mantis Legs and then deposit them in the corpse of a Giant Radscorpion. Go on. See what happens. Better yet, collect five of the legs, lure a Giant Radscorpion into Goodsprings Graveyard in the intro of the game (shoot the BB-Gun over the side of the mountain to get its attention), kill it and spam the Mantis Legs in and out of its inventory for a while... then when leaving Goodsprings, select to remake your character. Not only can you leave the tutorial at maximum level, but you get an assortment of extra perks for your trouble.
While, mercifully, most of the above bugs were patched by the time DLC rolled around, Old World Blues adds a delicious new bug in the form of the new Trait "Skilled." Skilled grants the player a permanent +5 to all skills in exchange for a permanent debuff that grants -10% experience. Already a good trade-off, selecting during character creation and then again with the "Remake Character?" option at the end of the tutorial will apply the bonus twice—but the drawback only once, making it easily eclipse every skill Perk or Trait in the game in regards to effectiveness. This can be repeated again in during Old World Blues itself when you are given one (and only one) opportunity to change your traits. This gives you a total of 15 points to all 13 skills. To put this in perspective, the maximum amount of skill points you get from leveling up is 17, and that is with 10 intelligence and a perk.
Honest Hearts brings a glitch related to the "Ant Misbehavin'" quest for the Boomers. The ants you're supposed to kill for the quest have eaten gunpowder and as a result will explode upon death if you hit them with pretty much anything other than regular firearms - but the .45 Auto Pistol and SMG will still blow them up on death.
Deathclaws will ignore you if their pathfinding can't reach you, even while you fill them with lead/lasers/nukes. While they react as most creatures would to a sneak attack (go alert and try to find the attacker), and even though they are perfectly able to see you, they'll never try to attack. Helps when clearing out Quarry Junction and the Deathclaw Promontory.
One that actually doesn't benefit the player but is amusing nonetheless: New Vegas has casinos and other areas where the player's weapons are taken away until they leave. Certain weapons are classified as holdout or "improved" holdout weapons and can be kept on the player if they choose to depending on their Sneak skill. ED-E's weapon is a built-in laser cannon, and so counts as a holdout weapon and is left alone... unless the player's Sneak is at 50 or more, since the cannon somehow doesn't count as an improved holdout weapon. Rex gets it even worse - no matter what your sneak skill, his teeth don't count as a holdout weapon and are somehow confiscated.
Wasteland has the super loot bags, filled with the rarest items in the game, the Red Ryder easter egg gun, and a lot of non-items with names like NAME and RUSSIAN. The NAME item is particularly useful: Depending on how you equip it, it can function as impenetrable armor or a gun with the maximum damage, and can be sold for $32,000.
The "Lure Glitch" in Dark Chronicle. You need to have recruited Olivie, two lures (which are bought from the aforementioned character), and the Lure Rod (which can be bought or invented). Equip Max with the Lure Rod and attach one of the lures to it, then in the status screen, flick the cursor over to either Monica or the Ridepod. Highlight the lure you didn't equip and by repeatedly mashing the X button, you can duplicate the lure attached to the rod up to 999. When you unequip the lures, they can be sold for an exorbitant amount of Gilda, and this can be repeated so long as you have two lures in your inventory.
A glitch in Secret of Mana on the SNES enabled a player willing to risk game save corruption the chance to fight the very first boss all over again - provided they made use of the cartridge's in-built soft reset feature - and obtain a ninth sword orb. As other ninth-level weapon orbs were dropped by enemies in the final dungeon, this was the only way to obtain the last forged incarnation of the game's legendary blade.
A programming oversight in Baten Kaitos Origins can make a large portion of the game much easier. Mountain Apples raise your entire party's HP by 5% each. The effect will stack if you take multiple. Given how you have about twenty free inventory slots and never need more than two or three slots open at any time, you can carry around fifteen or so apples and get tremendous boosts to your HP. Considering Origins is very Nintendo Hard, this is a godsend.
Not exactly a bug per se, but the Dreamcast version of Skies of Arcadia would start working harder (the system would make audible noise) just before a random encounter. This mildly offsets the annoyance of the random encounters, giving you a second to prepare for the upcoming battle.
The little-known "11th Chip Glitch" in Mega Man Battle Network 3. Used properly, this trick allowed you to use any chip in your folder at least twenty-one times, or as many times as you want if you only use that chip and know the secret. This included Mega Chips and Giga chips, which you could only use once, in addition to using this to break the four-of-the-same limit on Standard chips. This gets especially broken in White Version with the Balance Giga Chip, which cuts the Hit Points of everyone on the stage in half and cannot be blocked by anything. Combining this with the Woodstyle/Undershirt/SetGreen game-breaking tactic (referred to as "Cardboard Immortality" in some circles) allows you to reduce the Final Boss (and, for that matter, his powered-up form) to a simple matter of using Balance every turn while dodging attacks, then delivering a Finishing Move of your choice. The only downside to the 11th Chip Glitch is that it takes up a considerable amount of Navi Customizer space (at least three squares on the Command Line) and your backup programs are limited to Plus Parts, what little you can squeeze into the remaining Command Line squares, and EX Codes.
There's also 2's resident Game Breaker bug, the Gospel Duplication glitch. Anything you got between saving before the final battle and the end-of-game save was added to your pack in the end-of-game save when you picked it back up at the save point. However, one-off items were not considered taken by the game (with the exception of Power Ups), and so you could get multiples of the same one-off chip repeatedly. Common things to do this with were the very useful Roll 3 and Area Grab * code chips, both of which had set locations and were otherwise single-instance chips. This glitch also appears to let you buy chips for free, or at least those that are bought with Bug Frags, as the supply of Bug Frags is finite in this game, and you can buy multiples of the same chip (otherwise one-offs there) without taking a hit to your Bug Frag supply.
Also from the second game is the ElecBall chip obtained from a certain Metal Slime. It floats at an enemy, absorbing any damage it takes and then dealing it back to them. Electric attacks power up the attack and cannot be used to destroy it. On its own it's fairly normal, but there's a bug in the fight with MagnetMan that makes it deal 999 damage if it hits one of his attacks at the right time. And when you first fight him, he has 1000 HP, so...
In the 3rd game, you can customize your armor with 3 slot Countersnote this gives 50% chance that enemies that attack you will receive 50% of the damage dealt back at them. By the end of vol 3, you can use a character that was lost in the middle of the second game again. By that time, she will be around Level 90, while the last boss is Lv130. Said last boss has an attack where it'll go around to the background, and then come crashing into the battlefield, hitting everyone. For some reason, if this attack triggers a counter, it will trigger it three times. Due to how the battle system worksnote Levels are very important to calculate damage. If the attacker is at least 15 Lvs above the target, it will hit 9999 damage., if you have said Lv90 character trigger a counter by this attack, the last boss will be hit by 14997 damage and die instantly.
On the 2nd game, there is a part where you get to walk inside the Moon Tree's @home. In the last corridor just before the white hall leading to the fight against Innis, there is a small section of the wall that you can simply walk through. Here◊
In Mac Anu, if you run towards a specific spot in a specific wall, the floor suddenly vanishes, and all the other characters fall into the orange void. Here
Again in Mac Anu, there is a spot in the wall to the east of the dome that, if you ride your steam bike towards it continuously, the bike will start sinking into the floor. Here
Starting from the second game, there are 8 areas (4 on the beach, 4 on the mountains) where the Invisible Walls have a small break where you can pass, allowing you to walk into the air/sea.
If you use the steam bike while walking in the air, the bike will immediately start falling. If you use it on the sea, you will have a rather crazy run until you hit the water's edge, where you will start falling.
The area Delta: Flattening Ruined Fast Horse is pretty famous for its visual glitch. The treasure room is positioned too close to another room, so the two overlap. If you go to said room, it is possible to see a waterfall in the middle of the room!
The area Theta: Tranquil Black Moon Raven has a similar glitch, but not so pretty. Still worth looking, though.
In the second game, there are 4 areas that, if you use an item to teleport to a platform in a hill, you will end up inside the ground.
The last floor in the Delta: Upfront Starting Berserker is completely empty of enemies. There is a Battle Area in there, but if you enter, the victory sequence starts playing immediately without any fight. When you leave the area, it counts as if you didn't defeat 5 groups of enemies.
The area Delta: Screaming Idling Princess is a very interesting place:
It's a mirror of a quest area, so it doesn't have an objective.
The Side Quest NPC, Mecha Grunty, appears on the beach, almost in the water. This is the only area in the whole three games where this happens.
The 2nd platform does not appear in the map, and if you try to teleport to it, you can appear below the ground.
In the first game, there is a monster called "-" here that should not exist, and doesn't appear in the Book of 1000.
This monster drops an item called Healing Portion (portion, not potion), which should not exist in the first game, and does not appear in the Book of 1000. If you keep this item when converting to the 2nd game, it turns into a regular Healing Potion.
In Kingdom Hearts, if you enter Hercules Cup on a timer, pause the game and choose restart the match once you get to Hercules, the fight with Hercules will restart with the timer frozen.
In Chrono Cross, Lord Viper goes into a secret room in the bar at Termina at one point to receive his level 3 tech, FlagBearer, and an accessory, the Dragoon's Glory. However, if you step into the hall right outside the secret room without going into the main bar area, you can go right back in. Then, if you examine the place where the flag used to be, you will get another FlagBearer and Dragoon's Glory. The tech is useless to get multiples of, but the accessory is probably he best in the game. You can do this to acquire enough Dragoon's Glories to outfit the entire party.
Kingdom Hearts 2 has a bug involving Trinity Limit in the original Japanese version that causes it to always inflict the maximum number of combo hits. This makes fighting bosses a joke when you're dealing over 4 bars of their HP with a single attack in under 10 seconds.
Book Of Mages The Dark Times has a glitch where a single trip to the Mana Cave can grant you more skill points than you're possibly able to spend. In the early game, trips to the Mana Cave are the only way to level up at all; the upshot of this is that you can be almost as strong as the game's Bonus Boss before your first battle, completely removing any difficulty whatsoever for the entire rest of the game and allowing you to curb-stomp even the early Hopeless Boss Fight.
During the Inevitable Tournament in Breath Of Fire 3, you fight the first round in a pit of lava, standing on platforms held by large men called Dodai. You can win either by knocking out all three members of the opposing team or by knocking out the Dodai holding the opponent. The second member of the enemy team, Cawer, casts multiple spells, including Heal and Rejuvenate. Where this comes into play is how the enemy is programmed to fight - if you focus on their Dodai, they focus on yours. Cawer's AI isn't programmed to differentiate between healing spells and attack spells when attacking the Dodai (only when focused on you), meaning he can and will heal your Dodai if you focus on his.
In The Denpa Men 2: Beyond the Waves, there's the "Local DenpaM" glitch. For some reason, certain Wi-Fi signals cause the game's random character generator to flip out a little. It starts pulling characters from what seems to be a pre-built "pool" inside the game, which have predetermined appearances and all of whom have the glitchy name "Local DenpaM." However, all of these characters also come complete with decent-to-rare equipment already attached (a significantly rarer occurrence in "real" Denpa Men). They can be used to get good equipment early... and in some instances of the glitch, even if the men are caught and released, they will always appear with their trademark equipment, making them useful money farms as well.