In Columns, the playing field doesn't disappear when you pause the game, allowing players plenty of time to plan how to place their jewels, although this isn't much help when the field is almost filled.
The lowest difficulty setting, with only four kinds of blocks, virtually trivializes the Sega Master System and Game Gear versions, as they also have a particularly large playfield and game speed maxes out eventually (neither of which is the case on the Mega Drive). You can simply place the columns at some empty space without paying attention to their colors and will still be almost guaranteed to score a combo sooner or later; only your luck will determine when it's finally Game Over.
Some newer, official Tetris games (Tetris Worlds and Tetris DS, for instance), have a feature known as Infinity, which allows you to keep a piece active forever, as long as you move or rotate the piece before its "lock delay" timer runs out. This feature essentially allows an only-decent player to, with enough time and patience, max out the score in endless modes. It's only useful at the higher levels when pieces drop in an instant, but is still frowned upon for competitive play. This has been nerfed somewhat in Tetris Party and Tetris Friends, where the pieces will still lock in place after enough movements.
actually, in Tetris Worlds and Tetris DS, the infinite spin isn't as game breaking as it would seem. in Tetris Words, the object of the game is to clear 15 levels as fast as possible, and infinite spinning won't help you make any speed records. and in Tetris DS, several modes require you to lay down pieces as fast as humanly possible.
Tetris: The Grand Master 3 implements floor kicks, which allow an I block on a flat surface to rotate upright, allowing it to more easily slip into holes one block wide. This feature was not in TGM3's predecessors, which has led some players to believe that this ruins the challenge of the TGM series.
Some clones of Tetris, such as Blockles and TetriNet, have a multiplayer mode in which you can use items. One particular item, commonly known as "swap," has you trade stacks with another player. This can be abused by building your stack very badly on purpose and then employing the item. Heboris's versus mode has a similar item called "Copy Field," but the same tactic is useless because items are used upon obtaining them (by clearing the block(s) that have them) and the item only copies your field with your opponent's, rather than swapping, so that strategy is suicidal.
Puzzle Quest: Challenge Of The Warlords (and its sequels) has several examples, arguably made milder by the amount of effort it takes to gain and use them:
Items forged with the Rune Of Music add mana to each gauge with every 4 or 5 gem match. The Rune of Jewels boosts attack power with every full mana gauge. If forged with the higher level modifier runes (Rune of Dragons or Rune Of The Gods), equipping both type items can give you attack power equal to a Runekeeper's. And that's without using one of the tricked-out forged weapons (Rune of Axes, Rune of Swords).
Learned spells marked Very Hard, like Death Gaze (does damage equal to half the targets remaining HP), Petrify (2 missed turns to the target, plus an extra turn for every 20 green mana) and Spit Poison (Inflicts Poison and Blind status effects for three or more turns).
Similar to that, playing as a Fighter or Wizard and taking the Dragon Spider as a mount gives you access to the Breathe Fire spell, which does one point of damage for every point of red mana you have. Since both classes can raise their red mana levels ridiculously cheaply, you can end up with a spell that does upwards of 80 points of damage in one attack.
Combining spells for ludicrous chain damage: Such as the Wizard using a Lose-A-Turn spell (like Headbutt or Entangle), the Flaming Skulls or Berserk Rage spell (which both change red gems into skulls) and Finger of Death (changes a selected gem into a +5 exploding skull), letting a player extend a turn with 4 or 5 gem attacks (4 or 5 gem matches grant extra turns)
Some combos require you to go out of your way in selecting your items and skills. Take a knight. Level your green magic ability as fast as humanly possible (also, level your valor). You'll want to get it all the way up to level 20 (this could take hours, no one said snapping the game over your knee was easy). Then you go buy an Archliche Ring, a ring which gives you a point of every color mana if you match three purple gems. By this point, you will have skills that 1) turn every gem of a certain color into a purple gem, 2) double the number of gems, and 3) stun the enemy. With your points in valor, matching purple gems also gives you extra turns. Do this correctly, and you can stun-lock every enemy in the game (enemies with a high magic resistance might give you difficulties, but you can probably power through). As a bonus, purple gems double are additional experience, which means that you'll hit the level cap somewhere in the middle of the game after reaping your delicious purple harvest and matching hundreds of purple gems each game.
Of course, since earth magic isn't a favored skill for knights, you've got to put 3 of your 4 points per level into it and thus only boost it once per level, plus any skill points you buy (which gets expensive). Either way, you're looking at a stupid amount of grinding. Time to take advantage of the other major bug exclusive to the DS version regarding its random generator: or to be more specific, its utter lack of one. Every time you restart the game, the board is the exact same one, specifically one that allows you to get a +100 xp combo right off the bat if you let the computer go first. This works on every opponent from the lowliest goblin to the Big Bad. When used with the above knight/archliche ring combo, the +100 xp also conveniently fills your mana. Go wild.
Give the Warlock class the Doomknight's Burial spell (Turns all skulls and coins into green gems) along with Berserk Rage and its own Raise The Dead spell (converts green and blue gems to skulls, skulls to red gems, turn doesn't end). Combine them with the aforementioned Rune of Music/Rune of Jewels combo, and cast the spells in order "Burial, Raise, Rage." If none of the spells are blocked, if the attack doesn't kill the enemy directly, you'll probably have enough 4-skull matches left on the field to finish him off.
Galactrix has the Seventh Psi Power. The first six allow the player to become invisible to certain classes of ships, at the cost of some Psi Power points. The seventh makes you invisible to all on-screen enemies with no Psi Power cost. This, essentially, permanently turns off random encounters.
Puzzle Quest 2 has the Manticore and Wyvern poisons, which can only be wielded by the Assassin class. While the poisons available to the other classes max out at about 6 damage per turn (for 6-8 turns), the Assassin-only ones max out at 14 per for up to ten turns. And if you dual-wield different types (ex. A Hellforged Wyvern and an Ancient Wyvern), they stack. And poisons are ridiculously cheap to upgrade so you can max them out in short order. Once you've got two maxed-out poisons, you're pretty much invincible save for the bosses with instant kill moves.
In the teleportation game Portal, it's possible to poke the barrel of the portal gun through a portal, fire it, and pull back through the portal before the new portal forms. By repeating this, you can stay in one place while moving the far end of the portal further and further away. This makes several of the puzzles in the game much easier. However, all of the original game's challenges are possible without this trick.
This could also be done (and much more easily) in Narbacular Drop, the spiritual predecessor.
This was fixed in the sequel by forcibly pushing the player away from the portal if they fire a new one... which in turn led to a new trick using the "pushing" to launch players across space.
Even with this pushing element, it was not 100% accurate - meaning that a player could, with expert timing, perform the original stunt anyway.
Very rare for The Mario to be the game breaker, but Geolyte (the main character's planet and the Earth analogue) in Meteos is arguably this. For those of you not in the know, each planet in Meteos has its own attributes, such as playing field size and types of blocks that fall. Geolyte is easy to learn, but it also clears out blocks like mad, resulting in avalanches of garbage blocks for the opponent. In the sequel Meteos Wars, it gains the Planet Impact called "Gambit," which increases the size of garbage block drops for several seconds. Normally, you have to charge up a meter in order to use this, done by clearing blocks and clearing the screen. Geolyte can get rid of its blocks and clear the screen so fast that a sufficiently-skilled player can use Gambit again as soon as the previous one wears off, leaving the opponent stuck in a perpetually compromised situation.
There's also Hevendor, where blocks launched immediately leave the screen. While this eliminates any possibilities of chaining launches, there's room for more stacks, and if you have a Super Rocket and wait to fire it until those stacks get high...
Scribblenauts Unlimited features adjectives that you can add to items or NPCs to change their properties and behaviour. Adding the adjective "nonexistent" instantly makes the object disappear, which makes every quest that relies on the removal of something trivially easy.
Additionally, adding the adjective "deadly" to an object gives it the Touch of Death.
Super Sribblenauts had a limited version of the adjectives system. Normally, you could only add adjectives to objects you summoned. However, using a potion on any object will give the object all of the potion's adjectives, and potions aren't affected by most adjectives. You can make things indestructible, brainwash them, grant them superpowers or, using the right combination of adjectives, erase them from existence.
Fans in Scribblenauts can allow you to push distant objects
Many of the Action levels in Super Scribblenauts which are intended to required careful planning and timing can be bypassed by strategically placed objects with the adjectives 'indestructible' and 'immovable'.
In Angry Birds, there is the Mighty Eagle, which costs 99 cents to buy. It is summoned by throwing a can of sardines at the fortress & will plow right through every material the pigs could possibly build with, also causing an aftershock to kill any pigs that it missed. Pretty much, it will beat every single level it is used on.
Even more of a Game Breaker is the combination of the Big Brother Bird and the Super Seeds. These will guarantee total destruction, as a giant Big Brother Bird can break through ANYTHING and guarantee a win on a level with just one of them ... and unlike the Mighty Eagle, this combination is initially free. However, it's limited and the only way to get more is to buy more or hope that the "daily roulette" gives you more Super Seeds.
The first Knightfall game has the red armor. You are given a limited amount of points to clear the blocks out of the way, after which you start taking Scratch Damage (though given how fast damage racks up, it's very likely to kill you). The red armor lowers damage taken by 10%, meaning you no longer take damage from block clearing, letting go go up levels as long as you have the patience for it. Unfortunately, this was removed in the sequel.
Antichamber: The Red Gun's ability to turn as little as two cubes into a theoretically infinite number of cubes trivializes all of the puzzles that weren't specifically made with it in mind. Depending on how well you know the layout, this can be a lot of puzzles.