A Witch's Tale is an odd case because the New Game Plus is actually the real adventure.
The Legend of Zelda: The Wind Waker's New Game Plus featured Link playing through the game in the blue outfit he starts the game in (at the point where you would get the green tunic, you get invisible clothes instead). Also, text that was previously in the "ancient" language would be translated into English, revealing very interesting conversations (such as when the King of Lions boat is talking with Jabu, about Link, knowing he can't understand them.) As a third bonus, Link would start the game with the deluxe picto-box, making the picture-taking sidequest easier to complete. (Beware, though, as unlike most games, you can only replay this one once.)
The original The Legend Of Zelda takes it the farthest. The makers did some math wrong and only used up half of the available cartridge space for the game, and so had room to make the second quest an almost entirely new game, with the overworld and actual dungeons changing. It's also more Nintendo Hard, with Sword Beam-firing Stalfos, ways to permanently lose heart containers, and just generally more dev team sadism. You can also access this quest by just entering "Zelda" in the name selection screen, contributing to the birth of I Am Not Shazam for the series.
The Legend of Zelda: Oracle Games had a variation on this. When you beat one of the games, you can input a long, in-depth code to the other version (if you have two Game Boys and a link cable you can just link them up to do so). This allowed you to begin the second game with 4 hearts instead of 3, and very commonly, characters would give you secret codes, which could be used in the first game for some extra sidequests. Not only that, but the second game you play actually acts as a continuation of the story, and includes a different final boss. You can also bring over all the rings you'd collected in the other game.
There's also the "Hero's Secret" which is a more typical example- you start either game you played over, with all your rings from before, plus the extra heart even though you're starting at the beginning.
Zelda II The Adventure Of Link allowed you to replay the game from the beginning with all of Link's accumulated experience; once you max out all of your attack, life, and magic levels, any additional level ups would give Link an extra life.
The Legend of Zelda: Skyward Sword has Hero Mode, which carries over the treasures and bugs you've collected, changes some dialogue (mostly tutorial-related) and gives you the fully-upgraded Sword Beam from the beginning, but you take double damage and there's no health drops.
Though if you have enough time to New Game+ it, you probably have enough time to farm 100% souls in order to get the 100% item. Admittedly, Dawn of Sorrow had a weapon crafting system wherein you needed to give up several exclusive souls in order to unlock the best weapons, so a New Game+ would be advised for that.
In Okami, you have completion percentages in various areas of the game (treasures found, animals fed, weapons obtained, brush or battle techniques learned, godly miracles performed, sidequests finished, etc) and depending on how you did you unlock a large number of things for a new game plus, including "skins" for the character (a surprisingly large number of different forms, including one which is an animated pencil sketch), an ultimate weapon (of course), and of course the ability to start your new game with most of your old weapons, skills, money, etc.
Continued in Okamiden. Upon starting a New Game +, you get a spell that allows you to take the appearance of the Final Boss, as well as said boss' weapon as a divine instrument.
Beating Shadow of the Colossus unlocks a Hard Mode, as well as Time Attack options. Successfully completing Time Attacks allows you to gain magical items in what is normally an item-less game. Your stats will also carry over, and you'll need to beat the game multiple times if you want to build up the strength to climb the shrine to the top.
Activision's sandbox Western game GUN has a secret New Game Plus mode that can only be accessed by returning to the game's starting area (which takes some effort, as it is in an out-of-the-way place with no obvious way to return there), wading into a river, and entering a cheat code. Doing so adds a new "GUN" selection to the Options screen, a debugger-esque menu that allows you to watch any of the game's cutscenes and play any of the storyline missions with your endgame stats and bonuses intact.
Air Fortress has a second quest that immediately follows the first. After beating the first quest, you get a non-ending stating that the fortresses have all reactivated and you must go back and destroy them for good. The approach areas and fortresses are identical to those in the first quest; however, things are naturally more difficult this time around, and the destinations of most of the warp pipes are scrambled (radically altering your path through each fortress). Interestingly, the levels' and fortresses' colors are inverted as well.
After completing a Devil May Cry game once, players can continue on to the higher difficulties while keeping their weapons, upgrades and items. One exception is 1's Easy Automatic mode, where only another Easy Automatic game could be played afterward. 2, 3 and 4 did not suffer from this.
Clover Studios seemed to like doing this, as this was also the case with the Viewtiful Joe games, right down to the easy 'Kids' setting being unable to move on to more difficult settings after beating the game.
God Of War II offers a form of New Game Plus called Bonus Play, in which players who have already beaten the game once can start over (on the same difficulty level as before, or on any lesser level) with all the spells, weapons, upgrades and bonus items they had previously collected, in addition to selectable costumes and special abilities which can be unlocked in additional game modes or by finding hidden items in the game proper.
Also, doing this allows access to (and upgrading of) the already unbelievably overpowered Sword of Plot Advancement, the Blade of Olympus, (yes, upgrading a weapon that just killed a goddess) to fire lasers with every swing, and suck out the souls of your enemies.
The first game has unlockable costumes bringing different benefits. (for example, dressing like a cow gave Kratos infinite magic, while dressing like a businessman gave him double experience.)
The third game has Godly Possessions, collectibles that hold cheat options which can only be activated on subsequent playthroughs. A standard New Game Plus would have been problematic for this one what with the staggering amount of theoretical Sequence Breaking that starting with all weapons would have led to.
Ghostbusters on the Commodore 64. Completing the game and playing again with the money you earned was the only way to get the fourth car (which wasn't really worth it) or the third car and better equipment. Some versions like the Amstrad CPC one gave you a "bank account number", which was a Password Save for the accumulated money.
Finishing Cherry Tree High Comedy Club by recruiting at least three members allows you to start a new game while retaining your repertoire levels and knowledge of the candidates' likes and dislikes, making it easier to shoot for the Golden Ending by recruiting all six of them.
It's sequel, Virtues Last Reward does the same thing. However, it also adds the Flow system, which allows you to go to any scene you've already seen. This is necessary due to the increase in the number of choices the game has and the number of To Be Continued screens (called "Locks" on the Flow UI) the game has... the original game only had one of those (Ending B)), whereas Virtues Last Reward has somewhere in the double digits.
Beating Violent Storm on one credit unlocks the "Violent Round" mode, where you play the game all over again but with much more cruel enemy placement and Mortal Kombat style blood splatters from attacks.
Completing a route in Duel Savior Destiny allows you to use the cleared character in battles during the next route until by the time you get to the very last route you've unlocked everyone.
First Person Shooter
Black had an interesting kind of new game+. Complete the game on any difficulty to unlock "Silver Weapons" on that difficulty, giving you infinite ammo and unlocking the next difficulty. Also, if you manage to find every secondary objective item and explode every explodable thing in the hardest setting, you unlock on all difficulties: Infinite ammo, and the M16A2 assault rifle with unlimited underbarrel grenade launcher.
While Metroid Prime 3: Corruption doesn't let you keep your high-end weaponry in its New Game Plus, it does keep all the logbook scans and credits earned intact, which makes getting 100% Completion possible via multiple playthroughs, instead of having to do it all in one shebang. In addition, a Harder Than Hard setting is unlocked, so if the second playthrough is played in that mode, the bosses will grant extra medals that will further help the unlock of bonus material. Metroid Prime Trilogy adds this ability to Prime 1 and Prime 2, neither of which had a New Game Plus in their original Nintendo GameCube incarnations.
Wolfenstein adds a cheat menu to the game once you finish it once. The cheat commands include options that add Veil powers or unlock weapons instantly at the start of the game. By definition, this is an optional New Game Plus.
Postal 2 did one better: beating the game once unlocked both a cheat menu and "Enhanced Mode", which gave the player such bonuses as exploding sniper bullets and the ability to pissnapalm.
Call of Duty games starting with Call of Duty 4 do this, after a fashion, in multiplayer. Once a player reaches the maximum level, he can "Prestige," which put him back at level one. Later games made this a true plus, with Titles, Emblems, and extra custom class slots that could only be unlocked by Prestiging. They also added extra challenges that would only appear after a Prestige to make leveling back up faster.
Winning a game in the Diablo series opens up a higher difficulty levels for your now-experienced character. The gameplay doesn't change much, but the power of each enemy in the game does. In Normal difficulty of Diablo II, the low-level throwaway creatures in the starting areas die if you so much as breathe on them too hard; on Hell difficulty (the highest difficulty level), it's vice versa. In fact, it's entirely possible that a randomly spawned monster will be "triple-immune".
Hardcore setting: regardless which difficulty level you use, if your character dies, he/she's dead for good.
The eroge Brave Soul has a very developed version, where each game completion allows you to alter the difficulty and unlocks more options for bringing stuff over from the first game. As the game has nine endings, this is done to increase replayability. In addition, one girl is only available in a New Game Plus.
Super Robot Wars has had this for a good while, mainly to start over with lots of money to begin with. However, some have extra difficulties, just so your money is always useful.
The series also has a Special Mode, unlocked when you beat EX-Hard mode. It generally makes the game even easier than the series' New Game Pluses do, since you start out with at least one of every item and your units get more upgrade slots, but this also means it costs more money to get a unit's Full Upgrade Bonus. The Later OG games and the Z games have this partially, though with the latter the upgrade cost per bar is lowered making the total price closer to the original amount.
Some games outright carry over upgrades, skills, kill counts and some other thing depending on the game. Most Nintendo portable games have this.
A few even outright carry over level and UX carries over secret flags and unlocked secrets(!)
The Front Mission DS remake allows you to New Game + yourself into either easier or harder difficulties, as easy as 0.5x normal to as hard as 20.0x!
Pretty much present in the Armored Core series, for good reason. Mostly, AC games revolve around "missions", and in many games, missions "branch out", sometimes to entirely new endings. While not a New Game Plus per se, it allows you to replay missions you have done and do missions you haven't. This is even more useful in the third series (3 and Silent Line, at least) where missions often include "extensions", which are basically an entirely new (but optional) missions tacked onto your current mission if you perform well enough. The game treats it as an entirely new mission complete with briefings in the mission selector, with usually no prior way of knowing it other than the New Game Plus.
Not to mention that prior to 4/For Answer, most missions involve a lot of terrain navigating with hidden parts strewn around specific missions, often in the most unpredictable, out-of-the-way locations. The Mission Selector helps tremendously in this regard.
In a straighter example, getting a Human PLUS upgrade in the original series boots you back to the first mission with better performing upgrades.
Played with in the 4/4A series. The Hard Mode is only available in Free Play mode, which functions like the mission selector of old with one big exception: it will not replay missions that you have not done in the main storyline itself and the New Game Plus is largely present to unlock said missions. In the case of 4A, one must play a mighty five times just to get every single mission unlocked (three for the three endings, two more for the first ending's route that unlocks two out of three mutually exclusive missions, with the first one done in your first playthrough).
Zoids Vs. 2 (AKA Zoids Battle Legends) allows you to restart the "Zoids Battle" mode with all your Zoids and cash. You can even choose another character and play against different opponents. It's also the only way to afford top-of-the-line Zoids and parts.
Dungeons & Dragons Online lets a capped(level 20) character reincarnate back to level 1 with some modest to moderate bonuses on second and subsequent lives. The character keeps the same name, gender, and server, but is otherwise treated as an entirely new character by the game, being allowed to choose a new race and class. When a character succeeds in leveling to the cap once for every class, they get another moderate buff.
Kingdom Of Loathing lets you "ascend" after beating the primary boss; and start over. Access to previous skills and items depend on what Self-Imposed Challenge one gets. There are special rewards for completing higher difficulties.
World of Warcraft added the Death Knight hero class in the second expansion, Wrath of the Lich King. To gain access to this class, you must have already played a normal character to at least level 55. Upon doing this, you may then create a Death Knight character, who starts at level 55 in a zone unique to the class, with a full suite of equipment. After you complete that starting zone, though, you enter into the same leveling cycle as everyone else, with the exception that you've skipped pretty much all of the classic content. Ambitious players may wish to go back and do some of that content anyway for Achievements.
Unusual in that the reason had nothing to do with rewarding individual players - Death Knights were given a higher starting level both because of their origin story and because the developers wanted the new class to quickly have a presence in the end-game community (as content would now be created with them in mind). Being unlocked by leveling another character was just to prevent new players from skipping the beginning of the game.
In addition, Wrath saw the addition of heirloom items, armor and weapons that you purchase at maximum level and mail to alts, which scale with them as they level and are pretty much on par with or superior to the best available equipment for the level.
To a point, a character will frequently run into cases where an individual piece at or near their current level is superior, and once you got to 80, much of the gear you would be getting was superior. Mostly, it was a way to quickly grind a new character.
In a way, dungeons in World of Warcraft (and other MMORPGs) could be considered a type of New Game Plus. The first time through a new dungeon - especially end-game dungeons, you are likely to be underpowered and undergeared and likely to epic fail many times. Running through the dungeon gets you new, more powerful gear which makes failure less likely. For end-game dungeons this is pretty much required since you need the most powerful gear to even have a chance. For some players, going back through previously impossible dungeons and trying to finish them solo is a lot of fun.
Once you reach a high enough level in Billy Vs SNAKEMAN, you get the option of looping into a new Season, resetting you to the starting rank and level, but you keep most pickups that wouldn't directly cause Sequence Breaking (as well as a few that do), a chance to change your basic bloodline, and (the first, second, third, and tenth times you loop) unlock some additional content.
This gets turned up to 111 where you hit the cap at Season 111, and receive the appropriately named "Enough Already" Trophy
Star Wars: The Old Republic introduced the "Legacy" system with game update 1.2. A player's legacy begins with completing the first "Chapter" of any class's storyline, at which point the player may decide on a server-unique last name which will be given to any and all other characters on the same server as that character. From this point a player begins to earn "Legacy Experience" towards "Legacy Levels" and may also unlock special abilities and emotes, as well as unlocking certain other bonuses, such as EXP bonuses or other convenience bonuses.
Attaining level 50 with a certain race can Unlock that race, allowing a player to play as that race for classes which do not normally allow that race, such as making a Chiss Jedi. Attaining level 50 with a Human (which can be used for all classes in the current game) adds a small Presence buff for all characters.
Completing chapter 2 of a class's storyline unlocks the class's buff ability (each class has a unique buff gained at level 1), this buff can now be used on any character within that Legacy.
Completing Chapter 3 of a class's storyline (the final chapter, currently) unlocks a special ability which may be used whenever a player's Heroic Moment ability is active. These abilities are usually considered to be powerful or class defining. These moves are said to be learned from other members of the character's "Family", their Legacy.
The Mega Man Zero games had different versions of this (Hard Mode, Ultimate Mode).
Mega Man Battle Network 4 is the only Battle Network game that has this feature, with enemies being upgraded until the capping point after the third playthrough. Doing this three times, at the very minimum, is required to access the Bonus Dungeon. Ironically enough, despite the New Game Plus feature, 4 is often regarded as the worst game in the series to the point quite a few people who refuse to regard it as part of the series.
If nothing else, it is almost certainly the hardest game in the series if you don't use dark chips—Since the normal assortment of chips had to be spread out over three playthroughs, on your first run you will generally only get the level one version of any chip with multiple strengths, meaning both weaker chips and fewer chips and codes to choose from by the time you reach the endgame. And you'll have a fraction of the normal endgame health, regular memory and customizer parts. Killing the final boss with the chips available is a challenge. Each new difficulty does give you some new chips and new souls, but it also makes even the weakest enemies much stronger—by the third time you need one of a few killer combos just to kill the random encounters in the early areas, something which might be said for the Bonus Dungeon in some of the other games in the series.
The Classic and X series have a variation: you're not exactly starting over, but you can revisit any stage with all the weapons and upgrades you've collected. This is useful in Mega Man Powered Up, as you can unlock playable Robot Masters and different versions of Mega Man.
Each game in the Ratchet & Clank series has one. Players are presented with the option to begin a new game on the same save file, and are allowed to keep their ultra-powerful weapons and ammo. Considering how much currency the average player accumulates over the course of the average game (and subsequently spends on weapons and ammunition), this is pretty much the only feasible way for most players to get the first game's Infinity Plus One Gun, the RYNO.
In the first game, there is the raceway glitch that lets you gather said wealth with no effort at all.
Starting with the second game, Going Commando, the New Game Plus is called Challenge Mode, because the enemies get a massive power boost to match your stats at the end of the first game. Fortunately, you get to buy a whole new set of upgrades for your weapons to compensate. There's also the Bolt Multiplier, where you gain more Bolts as you kill enemies without taking damage.
Shovel Knight allows you to play again with all of your upgrades, but makes up for it by ramping up the difficulty.
Spyro 2: Ripto's Rage! allowed you to play a new game with a permanent Super Fireball enhancement after beating the game with 100% and acquiring the enhancement in the very last level, saving, and starting a new game in a different save spot.
Also occurs in the rebooted continuity of The Legend of Spyro: The Eternal Night in which completing certain tasks allows you to replay the game with access to the Dark Spyro ability which shortens the playtime considerably (amusingly, Spyro also appears in his "dark" form during the cut scenes.)
In Sonic The Hedgehog 3 and its sequel Sonic and Knuckles, if you complete the game, you can go back to that save file and replay it with all the emeralds you have picked up so far. If you got all the emeralds the first time around, you can play as Super/Hyper characters from the first zone.
In contrast, Metroid Fusion and Zero Mission only have unlockable higher difficulties - but these come with the added bonus of an item counter and timer added to the map screen, making 100% Completion and speedruns that little bit easier.
Super Mario Land: Beating the game once unlocked the harder mode. Beating the game again after this would allow a stage select... although since the game had no saving whatsoever, both of them are of questionable use.
If you start another game on Super Mario Bros 3 immediately after beating it once, the game starts with an inventory full of P-Wings, which gives you infinite flight for one level after activating it, then turns into a regular raccoon suit afterward.
Doing the same thing in the original Super Mario Bros allowed you to play the game with all of the Goombas in the game being replaced with Buzzy Beetles. In the original NES version, this is accompanied by a level select, but in Super Mario All-Stars, each of the harder levels, which are labeled with stars in the file select menu to distinguish them from the regular versions, has to be unlocked (though this isn't much of a big deal since there's a save feature in that version); in other words, the harder version of World 1 is the only one of them that is available after beating the main version of World 8 (the ability to replay the standard versions of worlds isn't affected; the harder versions are listed after them in the world select portion of the file select menu).
In Super Mario Bros.: The Lost Levels, if you played through the main game without warping, you accessed the Bonus Level Of Hell World 9, which you only had one life and no continues to complete. Furthermore, each time you played through the game, you earned a star. Once you get eight stars, you go to Worlds A through D, at the end of which you finally find the Princess. The All Stars version changed this slightly, as you don't lose all your lives in World 9 (you still can't continue), and you go straight to worlds A-D after the first loop.
In Super Mario Galaxy, if you get 120 stars, you're given the chance to play through the game again- as Luigi. (Luigi jumps higher than Mario, but he has an annoying tendency to slide when he stops running.) Get 120 stars again, and you'll unlock Grand Finale Galaxy, where you can get the 121st and final star (with both Luigi and Mario).
In Super Mario Galaxy 2, getting 120 stars will unlock the 120 Green Stars, and getting those will unlock the Grandmaster Galaxy. Beating it will unlock "The Perfect Run."
In the first Kirby's Dreamland, an "EXTRA MODE" opens up after you've beaten the game. (Actually, you can get to it at any time, but beating the game tells you the Classic Cheat Code to activate it.) It features harder enemies and massively ramped-up bosses, with not only more health, but much faster, more erratic attack patterns. Beating that lets you see an enemy reel.
Kirby: Nightmare in Dream Land for the GBA (a remake of the NES' Kirby's Adventure) gives you one if you beat the original game 100% (which means finding all the hidden bonus switches), where Kirby has half his normal health. Beating THAT 100% unlocks a mode where you can play the game as Meta Knight.
The Meta Knight campaign is also featured in Kirby Super Star Ultra after completing the Revenge Of The King subgame, covering the original main subgames in the SNES version.
Inverted in Tale Of Tales' artpiece The Graveyard. (They seem to be very fond of inverting game tropes.) You play an old woman who visits a graveyard. The full version of the game is exactly the same as the trial, except, every time you play she may die. The typical "new game" button shows up then, but if instead you prefer to quit the game, you'll find out there is no built-in option for that: you have to crash the game from the OS or reset the computer. If you do so, when you enter the game again... she will still be dead.
In Ghosts N Goblins and its sequels, defeating the final boss of the first loop gives you the message "this room is an illusion" or something like that, and sends you back to the start with a higher difficulty. To reach the True Final Boss and ending, you must find a certain weapon along the way.
Similarly to Ratchet, from game 2 onwards Jak and Daxter players could access Hero Mode as an unlockable extra, in which you go through the game with all your big fancy weapons and power upgrades. In The Lost Frontier, the only game to offer it as soon as you finish rather than shortly afterward, there is a special plane - the Jaguar - that can only be accessed in Hero Mode. Hilariously, unless you are a very dedicated grinder or have almost superhuman ability to streamline your purchases, you will likely be unable to afford the maximum upgrade to the Armageddoneven after going through Hero Mode once.
Mirror Mode in Donkey Kong Country Returns. When playing a level in this mode, all items you collected (puzzle pieces and KONG letters) remain as such, so your goal is to simply reach to the end. Easier said than done, however. Donkey Kong cannot be helped by Diddy or the inventory items, and he only has one HP.
The WiiWare and Steam versions of Cave Story has Curly Mode, which lets you play through the game as the main character's partner, Curly.
If you got gold on every level in HarmoKnight, the game lets you play those same levels, but fast. (This is optional and only required for 100% Completion.)
Real Time Strategy
The early online RTS NetStorm had this as a main gameplay mechanic. As you gained levels you received new units, but once you had all units you were given an option to restart. You'd lose everything gained from leveling, except now your weapons do 10% more damage.
Space Channel 5 offers a unique variation of this trope: Almost a third of the game's content is automatically skipped on your first playthrough, and playing the game again in Extra Mode after beating it once grants you access to several hidden levels.
In Elona, once your Relationship Values with one of your Monster Allies gets high enough, you can marry the ally (regardless of its species) and then "make a gene" with it (regardless of its sex or species). You can then "incarnate" the gene into a new adventurer, who will inherit copies of all the items you were holding in your inventory when the gene was made. The new character still has to do some Money Grinding, though, since each item you inherit requires buying an "heirship deed".
Role Playing Game
Naturally, Chrono Trigger, as listed and pictured above. You keep anything that's not a keyitem in the new game, so you can fight the final boss almost anytime, required to get the various endings. Chrono Cross not only has this mode too, but it's the only way to get all of the 40+ playable characters at once. Cross also gives you two extra items: one lets you switch Serge for another character in battle, and one lets you speed up or slow down the game speed, which is a godsend. The US version of Chrono Cross and the DS version of Chrono Trigger also add Bonus Bosses that can only be fought in New Game Plus.
Lufia II: Rise of the Sinistrals offered a new feature when starting a game after beating it once called Retry where experience and gold gained was quadrupled(!), not only making the game far and far easier but allowed to beat some bosses you normally couldn't feasibly hope to beat. beating the game again gave you Gift mode where you could do the bonus dungeon with any set of characters you would choose.
Once you have won the game once, Mass Effect 1 lets you start a new game with the same character, inventory, and experience, so you aren't forced to use a new character when playing on the newly-unlocked Hardcore difficulty. The game even increases the level cap from 50 to 60 for both old and new characters. Similarly, winning again on Hardcore unlocks the Insanity difficulty, with the same ability to play using an old character. Furthermore, some unlockable bonuses let you give a new character a bonus ability or weapon they cannot normally use—for example, giving assault rifle training to an Adept, or giving Singularity to a Soldier.
The New Game Plus in Mass Effect 2 is, to many, of very questionable value. You keep your level, your weapons (including heavy weapons), armour pieces, and you receive 200,000 credits and 50,000 of each resource. Problem is, you don't keep your Paragon/Renegade levels, you don't keep any of your upgrades, and, since the game scales relative to the player's level, the game is significantly harder. The Paragon/Renegade checks are much higher, meaning it is nearly impossible to resolve the Miranda/Jack and Tali/Legion fights without being close to or at 100% of either level. Compare to starting a new game with a level 60 import from Mass Effect: you start at level five (out of thirty), already have a decent number of Paragon and Renegade points, have 350,000 credits, and 60,000 of each resource. Worst part? The 200,000 credits and 50,000 of each resource are available for all new games once the game is beaten. It's actually best for you to just play your Old Save Bonus again.
Also, if you went for 100% Completion, you're probably pretty close to level 30 anyway. With all the DLC and an Old Save Bonus character, there's more than enough XP to get to level 30.
Mass Effect 3 continues the tradition much the same as the previous game in the franchise, only this time the level cap is 60 again, and a new character you probably won't get anywhere near on your first playthrough. This may sound well and good, but keep in mind that this time your Old Save Bonus imports your level too, so if you hit the last game's cap of 30, you'll start at 30.
Beating Mass Effect 3 allows you to start a New Game Plus using a previous save, which starts you off with your level, weapons, armor, and weapon mods you've obtained in that save, as well as increasing the weapon level cap from 5 to 10.
Obtaining certain DLC achievements in Dragon Age: Origins rewarded you with powerful items, which were given not only to the character who obtained them but also to every new character you create for that account. Which made the supposedly dirt-poor, lowlife characters start the game with massively overpowered artifacts and tons of gold (once you reach the first vendor at Ostagar) in their backpacks. Dragon Age II mediated this a little: while the bonus starting items remain powerful, they all cost next to nothing at vendors and quickly grow obsolete, since all loot now scales with the character level.
Final Fantasy X would let you keep you Al Bhed primers from previous playthroughs, if you went to the Al Bhed sphere as soon as you landed in Spira. If you had mastered the language in a previous playthrough, this made early scenes easier to understand. It also let you get the special item from Rin's quest earlier.
Furthermore, the non-American released International version of the game contains a glitch in the end-game that allows the player to replay the last third of the story with all their new weapons, powers, and equipment. It is performed by beating a Bonus Boss and then glitching your way past an NPC that blocks the now-destroyed Al Bhed home. Accessing this normally restricted area sets off an Event Flag, and the game acts as if you're visiting there for the first time. Most players take great pleasure in killing That One Boss in one hit.
Final Fantasy X-2 had an actual New Game Plus option. After playing through the game once, it would save after the cinematics. You could then use the New Game Plus option to starts a new game, being reset to level 1, but retaining all your obtained Dress Spheres, Sphere Grids, Accessories and Completion Percent. This was an essential part of obtaining the Perfect Complete ending (requiring 100% or more) as there is a choice in the middle of the game that limits your game choices. On your first play through one path gives up to 100% completion, while the other gives up to 99.2%. (In fact, if you complete both paths completely, you technically get 105%, but the game only lists 100%.)
In Final Fantasy XIII-2 after completing the game and after the credits roll (or are skipped), you are returned to the Historia Crux, awarded CP and the Paradox Scope Fragment Skill, and are allowed to continue from right where you left off.
The International Version of Final Fantasy XII has 2 modes: New Game Plus and New Game Minus. New Game Plus is achieved simply by beating the main game, and while nothing carries over, all characters start at level 90, making the game substantially easier (though not as much as you think, as the game is extremely gear-dependent for damage and defense). New Game Minus is unlocked for completing Trial Mode, and puts all characters at level 1 and have them gain no experience.
Final Fantasy IV DS has a new game plus mode after you've completed the game, it also unlocks the Limit Break augment, which enables characters to surpass the usual damage cap. Unlike most of the other entries here, though, you can only play through the game three times on one save file, giving you a max of two New Game Pluses.
Possible in Wild ARMs 4. You can carry over items, including the [ROMs] you need as part of the quest to find the Bonus Boss, which can also be obtained by using a save file from an earlier Wild Arms game.
Also possible in Wild ARMs 3 as long as you collect at least two EX File Key items during the course of the game. Only levels and gella (currency) are carried over, all items and abilities are lost.
Wild ARMs XF: Beyond keeping your levels and equipment, you also get an experience multiplier for each playthrough. So you get double experience on your second playthrough, triple on your third, etc.
The GBA Golden Sun games do something similar; with an EXTREMELY long code, it is possible to keep all of your djinni, items, money, and stats from the first game when playing the sequel. This is the only way to complete Golden Sun: The Lost Age with 100% Completion, as certain items and djinn aren't available in the second game.
Completing The Lost Age unlocks the game's Easy mode (you keep all acquired experience) and Hard mode (tougher bosses).
If you have a friend with a GBA (or if you have two of them), you could link them together and do a simple transfer. Also, The Lost Age's easy mode isn't too much easier; without your Djinn, your party is pretty weak.
Demi Kids (a Lighter and SofterShin Megami Tensei game for Game Boy Advance) actually had three options available to you once you beat the game. The first let you go back in time to just before fighting the boss. The second was the New Game Plus mode, where you started from the beginning, but with all your demons, inventory, level, etcetera—however, your partner would be returned to its first stage, so doing this over and over again is the only way to see all its stages. Finally, the game offered you a Playable Epilogue, which not only brings all your friends back from the dead, but allows you to get muddafriggin' SATAN as one of your Mons.
After you beat the game, Devil Survivor lets you start again from the beginning, with all of your demons, cracked skills, auction levels, and macca. You don't keep your character levels, but the Anti-Grinding is disabled, so you can get them back faster than you got them the first time.
Persona 3 had a new game plus that is considered a Gamebreaker by fans of the Mega Ten series (which is normally considered much more difficult than other RPGs) by the virtue that the New game starts with the main character at the level he was in the final save, all his weapons, money, and a record of all the Personas that have been created.
The Updated Rerelease, Persona 3: FES, allows the player to import the main characters status (his non-combat skills, that is), any items gained from maxing out a social link, and a record of all personas registered in the compendium. Needless to say, this made maxing out social links the second time much easier, as well as saving a lot of time building up personal skills.
Persona 3 Portable's New Game Plus also includes the option to choose which person you spend your dying moments with at the end, provided you maxed their Social Link and for the Female Protagonist, made it romantic.
Persona 4's new game plus only allows the player to keep his money, characteristics, persona compendium, and the max social-link items, starting him at level 1 as always. This essentially renders Izanagi-no-Okami (the ultimate persona of the game) a useless novelty, since the player would STILL need to grind to level 91 to actually summon the damn thing.
While level isn't carried over, the max level of persona you can summon IS (oddly though, you still can't fuse a persona above your level), so you can go ahead and summon the Trumpeter with immunity or better to everything.
Many people are unaware that the version of Persona 2 released in the USA (Eternal Punishment) was actually the second half of the game, and if you played through the first half (Innocent Sin), you could import your Tatsuya character to EP with his stats intact (not possible with anyone else for obvious plot reasons). His last name, if changed from its default (Suou) would also change for EP, along with changing his brother's last name to the one that you chose. However, since the PS1 version of Innocent Sin was never brought over, the feature was removed in the American version of Eternal Punishment.
Digital Devil Saga lets you keep your mantra grids. So you might actually have a character with all mantras mastered...if you money grind like mad for 2 or 3 playthroughs.
Strange Journey lets you start with your money, weapons, compendium, unlocks new apps and lifts the level cap for fusion.
Well... pretty much all of them since Shin Megami Tensei: Nocturne, actually; that one had the Amala Grave Run, which if don properly would net you an extra Press Turn. And it always makes subsequent playthroughs WAY easier...once you get the money to resummon stuff from the compendium.
The original Boktai let you keep all your items, Frames, and Lens levels and is necessary to claim the Dark Gun and the Dark Emblem (which the latter is required for the Bonus Dungeon boss). Lunar Knights let you keep your items on a New Game Plus. Keeping your levels and stats is optional.
Breath of Fire: Dragon Quarter took this a step further with its Scenario Overlay system. You can restart, or return to your last savepoint at any time, losing party levels and story progress, but keeping money, equipped items, skills, and stored items.
The team who made this moved on to work on Dead Rising, which uses a similar mechanic.
In Odin Sphere, you can replay all of the character's stories (and the last one) after they've been completed. Considering how difficult it can be, it's probably a good idea to do this.
Suikoden IV and Suikoden V also have included the option of a New Game Plus, though SV's is more of a bonus. While Suikoden IV only lets you keep money and items in your inventory at the end of the game, Suikoden V let's you keep not only those, but Party SP (though oddly enough, not the personal SP of your characters, which is reset to 0), items in your storage, epic skills you've acquired, formations, the various skill manuals (which allow your party's combat and magic trainers to raise your skills to higher levels) and even allows you to run faster than normal when holding the Triangle or R2 buttons. The only downside is that neither game transfers over the equipment or runes your characters had currently equipped (everyone has their normal default equipment instead), which is quite obviously the best stuff you'd have. Also, weapons are all back at level 1.
Shadow Hearts: Beating the game allows you to keep your Harmonixer forms from the very beginning....even the ultimately powerful Seraphic Radiance. Only problem is obtaining enough SP to do so.
The World Ends With You has a version of New Game Plus that's even better than most: once you've beaten the final boss, you can jump to any chapter of the story at any point, even if you're in the middle of a different chapter, with your level, your items, your pins, your friendship levels, and so forth intact. Want to fight some Noise that only appear in chapter seven, but don't want to play through chapters one through six? No problem!
They also let you skip through conversations at super-speed by holding down a button. Which is helpful, considering how talky most of the characters are.
And since you can pick your partner at any time that you're not in battle and take Infinity Plus One Equipment that you only get at the end of the game into earlier chapters, WEWY 's New Game Plus takes Gameplay and Story Segregation to a whole new level. For example, you can play as Joshua in the first week, even though you don't meet him until the second week, or easily demolish bosses in Hopeless Boss Fights...only for the following cutscene to depict your characters as getting their behinds handed to them!
The Icewind Dale series has "Heart of Fury" mode, which was designed for characters that have completed the original campaign. In this mode, enemy stats go through the roof. While it's possible to start Heart of Fury with level 1 characters, successful completion is another matter.
Tales Of Symphonia's New Game Plus allows players to spend excess "grade" (earned during combat) for various features, like keeping the previous game's Relationship Values, recipe ratings, techniques, etc., or raising/lowering grade and experience growth rates.
On the second and further playthroughs of Tales Of The Abyss, each character gets a second Mystic Arte, along with the bonuses mentioned above in Symphonia's entry. A couple sidequests and dungeon also open up, and you have to play through at least twice to get one hundred percent completion (as there is one sidequest where you choose what reward you get, and two aren't found anywhere else).
The New Game Plus Grade shop has pretty much become a staple of the Tales Series. New Game Plus only dungeons have become pretty common in the series as well.
This is done in Sonic Chronicles. You have to unlock all the characters again, but you can re-choose their stats and abilities they they would have earned up to the level they are at. The main point of this particular game is that you can take different dialogue choices, and use different characters without worrying about having the best party for each particular area.
Valkyrie Profile 2 Silmeria puts extra "crystals" on your title screen each time you beat the game. Each crystal makes the enemies slightly harder.
Eternal Sonata does something similar with Encore Mode, making all enemies 1.5x as strong, though the amount of experience gained remains the same. You are, however, allowed to keep all Party Levels you have already gained (either Party Level 5 or Party Level 6 depending on whether you visited a certain optional dungeon) and also keep all music pieces from the game to listen to in the menu, as well as all Score Pieces from the Score Piece sidequest. Additionally, in the PS3 version, you get to keep all of the alternate character costumes that you've found. You also get to keep the Hero's Crest item that opens up the previously mentioned final dungeon. Finally, playing Encore Mode opens up a number of new sidequests by providing you access to a portal device that allows you to revisit all areas you've been to previously. (In the first playthrough, this device allows you to travel to a particular area to continue the plot, but the part of it that would allow you to travel back to other places is broken down.)
Valkyrie Profile: Covenant of the Plume requires you to get all three endings to unlock the bonus dungeon. You also get to keep skills gained from granting Final Death to your allies, as well as any of your endgame equipment, and equipable and usable skills.
Multiple variations in Titan Quest. Like Diablo, Titan Quest allows you to take the same character through three different, successive difficulty levels. In addition, the Expansion Pack adds a 'transfer stash' that allows you to transfer items between completely different characters. This can result in a melee character finding a good bow, placing it into the transfer area, and starting a new game as an archer character. Assuming the archer meets the items' requirements, he/she can then start out the game much more powerful than he/she could have had they been the player's first character.
Baldur's Gate: Dark Alliance and its sequel provide a similar feature in two different ways. First, in any game you may load characters from a different game, meaning you can load your end-game character at the very beginning of a new game, giving you access to awesomeness from the beginning and letting you level further than the normal game allows. The second way is that if you beat the game on certain modes it will provide you with new characters and also the Extreme difficulty level, which lets you use your end-game characters and has the same creatures as in the other difficulty setting but with levels high enough to challenge you. Level 25 rats, anyone?
The original Baldur's Gate exported your character data (equipment and inventory included) immediately after the Big Bad goes down. You could then start the game all over again with your leveled-up character. It is fun to try but since you've probably already reached the level cap on the first play-through and the game is balanced so that with a right character build, you can insta-gib most starting enemies from the onset, you probably won't need it. That character export is actually intended for you to import in the sequel so you can start with your familiar character rather than having to create a new one.
X-Men Legends allows you to pick different "skins" for the characters after the first playthrough. Meaning you can have Wolverine in his yellow spandex, or even a human Beast. The pictures and in-level cutscenes will reflect any costume changes you make.
Luminous Arc carry over your characters' levels, learned skills, Rico (currency) and Heart Levels. There's also an New Game Plus only dungeon unlocked.
Luminous Arc 2 allow the player to go through the game again with all the items, equipments and levels they have at the end of their first playthrough. Also, they can use any of the playable characters to participate in any battle (save for a few). Meaning it's possible to have Fatima and Josie go against themselves. Naturally, this has no bearing on the plot. Other than that, you can get the other ending.
Demon's Souls starts your character back at the beginning of the game after beating it, with all the stats, items, and equipment you had at the end. However, all the enemies are considerably tougher as well, in a game not known for being very forgiving in the first place. Going through the game more than once is actually necessary to collect all the weapons and spells that exist in order to get some Playstation 3 Trophies.
Subsequent New Game Plus runthroughs, after the first, also increase the difficulty, but not as much as the first time. By your third playthrough, you'll notice enemies are not as tough, and by the fourth playthrough, you're likely to be breezing through the game.
Legend of Mana carries over all equipment, techniques, items, and Cactus Diary entries, but everything else has been reset, so you'll have to replay the necessary sub-missions in order to build your map.
You also can choose harder difficulties, including Nightmare (enemies' levels are 30 levels higher) or No Future Mode (all enemies are Level 99!).
You also get to keep any of the special locations you acquired for your home, like the Workshops and any pets you gained for the ranch.
Neverwinter Nights allows you to export your character at any time during the game, to be used in other modules. But you can also start a new game again in the main story using your leveled up character. Making much of the beginning of the story much easier.
After completing Atelier Annie, you get to start again from the beginning with all of the items you've created up to that point (though you will still have to rebuild all of your resorts and friendships from scratch).
The PC version of Jade Empire has Jade Master mode, essentially allowing you to import the character you finished the game with back to the start with all his stats, styles and techniques retained- but back at level 1 for experience purposes. Weirdly, the initial "training" fight appears to be set up to ignore stats- so a trainee at your character's school can quite happily deal over 1000 damage with a single attack...
Marvel Ultimate Alliance allows you to load characters from your other save files when you start a new game. Good thing, too, as you will have a hell of a time getting through hard mode with fresh characters...
In Infinite Space, your level and money will be carried over to your next run, but you have to hunt down the blueprints again. Also, some blueprints are only available if you have finished the game once.
Romancing Sa Ga: Your jewel reward for each quest in each future playthrough increases, you keep shop levels: Allowing you to buy high end gear early on if you can afford them. The times you talk to Schiele carry over; allowing you to fight Schirach later on, if you cleared the quest already, you only need to talk to her once in each future playthrough. If you cleared the ecology quests, you are given the option to fight the corrupted versions of the Elemental Lords, which drop unique equipment. 2 New characters become available if you fulfill the right conditions For Darque, you have to defeat Scorn, clear the Assassin's Guild quest and meet Death all in the same playthrough. To get Aldora in her original body along with her legend, you need to have Aldora as Darque's dominant personality (Reach 50 INT) and clear her related quest, then defeat Saruin to unlock her. Purgatory is also unlocked in future playthroughs as well if you undertake Aldora's quest.New Game Plus also unlocks the ability to power up Saruin by offering the fatestones to him in the final dungeon located where you fought the minions for the last time.
Resonance of Fate has two versions of New Game Plus: Play through the game again on the same difficulty with pretty much everything from the first playthrough (levels, guns, items, white hexes, etc.), or play on a higher difficulty level, where enemies have more HP, while retaining few things from the prior playthrough. You can continue to beat the game and access higher difficulty levels, up to a difficulty where enemies have 5 times as much health as the first playthrough.
Recettear An Item Shops Tale has a variant in that you get to start each new loop with the same items and character levels whether or not you're able to make it all the way to the end of the game (five weeks in game time). You still start the game on Day 2, Recette's first official day at the shop, and have to go through all of the dungeons and meet all of the characters again.
Torchlight lets you start over after beating the Final Boss. The first re-start opens the infinite dungeon. Every re-start lets you improve one item and gives you one free fame level (skill point), plus the same storage that lets you pass items between characters works across the generations.
Etrian Odyssey III: The Drowned City allows you to start the plot over with your experienced guild, enabling you to pursue the Multiple Endings and their rewards however you choose, as well as unlock both the Shogun and Yggdroid (which are normally mutually exclusive).
Summon Night Swordcraft Story 2 features a New Game+ system that basically carries over everything that won't break the game. You get to keep Craftknight rank, fishing points, money, you get some cool extras depending on what you did in-game, as well as an equip at the beginning that raises the amount of EXP you get. You don't get to keep your level for some reason(if you're taking advantage of the New Game+ system here to begin with, you really don't need to), but to make up for it, inside the Fire Fortress are 5 chests; these chests can store 5 weapons of your choice, as long as they weren't made with the Gem of Light. So basically, you can store your incredible elite weapons that can take down the final boss in 20 seconds for the future you to gush over, and proceed to murder the last 2/3 of the game with. Much exploitation then follows.
In Dark Cloud 2, if the player aquired any of the alternate clothes for the characters (which they wear in cutscenes), a new game can be started with any of the aquired clothes, so long as a game save that has them is present on the memory card. You can also save pictures into an album (found in Max's house from Chapter 2 onwards), which can be accessed in any save game where the album is in the inventory. If you save certain ideas and scoops into the album, you can invent and build things that you wouldn't have been able to until later chapters, like the Ridepod's best equipment, or some particularly powerful weapons for Max and Monica.
Nie R's New Game Plus allows the players to understand the Shade's speech as well as hear Tyrann along with the usual extra endings. The result is that it makes the entire game a mix between Fridge Horror and You Bastard.
It also starts you at the half way point of the game.
Sengoku Rance is a Strategy RPG / H-Game with detailed New Game+ options. Completing each of Sengoku Rance's main endings and accomplishing several bonus objectives unlocks a permanent bonus point pool for a save file. These bonus points can be spent for powerful items, special generals, and assorted goodies on future playthroughs.
Bastion's NG+ mode lets you keep all of your experience points, weapons and weapon upgrades from your previous playthrough, as well as most of the Vigil rewards (you still have to redo Proving Ground challenges for them to count in your NG+). You can also restore some of the late-game buildings, such as the Shrine and the Vigil, at any time you want.
This is also a rare example of the NG+ being justified in game, as the NG+ all but says outright that the Bastion's Restoration function failed to stop the circumstances leading to the Calamity, trapping the characters in an endless cycle of saving the world until things somehow go right or they use the Evacuation function.
Both Breath of Death VII and Cthulhu Saves The World unlocks additional game-modes after the first play-through. Both games has Score Attack, where you get points the lower your level are compared to a boss when you beat it, and Cthulhu adds Overkill (a single battle is enough to get you to level 40) and Highlander (only one character can be in play at any one time, but XP gains are massively raised) modes. The PC version also add an alternate campaign, Cthulhu's Angels.
Dark Souls, much like Demon's Souls above, has enemies become noticably more difficult in the first New Game Plus run with slight increases in difficulty afterwards. To make things slightly easier, New Game Plus allows characters to retain all of their equipment and stats (barring key items) and bonfires retain their kindling level. At least three runs are required to obtain every achievement in the game.
Alpha Protocol has a New Game Plus mode that can only be unlocked by playing as a Recruit, where Mike starts off with no skill points in any category. After which he can play as a Veteran, in which he starts with three points in every field and unique dialog pertaining to his increased badassedness.
Continuously, and aggravatingly, averted by Pokemon. The only way to preserve your collection of mons is to trade them into another copy of the game, and in Pokemon Black And White, you can't even do that until beating the first Gym in the new copy. However, there are some exploits that let a player create a New Game Plus style experience: 1) Use TMs in the old game to teach powerful moves to the new guys before trading them in. 2) Use Pokemon from the old game to mule items and Vendor Trash over to sell. Since the game gives you the Dragon trio's Orbs for free, you can send them across (assuming your Dragon trio has theirs already) and sell them for a cool P15,000. Full Restores also make a good store of value for transferring your endgame money, since they are the most expensive purchasable and tradable item at P3,000, and sell for P1,500. 3) Since they're traded, your new team will Level Grind faster, though this can be a problem early on, as their levels will outstrip your badge collection and cause disobedience.
It is possible to do in the first generation, with the help of Pokémon Stadium or Pokemon Stadium 2, which allow you to store Pokemon on the console game and transfer them easily. However, second generation games have to wait until they've caught 150 species of Pokemon before taking transfers from different cartridges, and the console-based storage programs for all the later generations locked out the option completely. The more optimistic way of thinking would be that this was because Game Freak thought having an easy method of mass-transferring Pokemon within a generation would be too much of a Game Breaker; the more cynical perspective would be that they wanted to force people to buy the game again if they wanted to replay without losing everything.
Lionheart: Legacy of the Crusader had a variety of this in which it is not neccesary to complete the game. At any point in the game, players can export their characters. These characters can then be used to create a new game; keeping their skills, attributes and perks but losing all items in their inventory.
Kingdom Hearts 3 D allows you to carry over your Spirit companions from another save, though the only things they retain are their rank and affinity level. This can effectively give you access to virtually every command and ability in the game from the get-go if you're willing to grind a bit on the Water Barrel minigame.
Shoot Em Up
Star Fox Command limits you to one of the possible nine endings for the first playthrough. That's right, nine endings. The only thing that makes this sort of a New Game Plus however is the first level changing two times when the mode is completed several times.
Many Shoot 'Em Ups have New Game Pluses in the form of multiple "loops"; after beating the game once, you start over again, with the game at a higher difficulty level. The Gradius series in particular has this as a norm. If you meet certain conditions in Nintendo Hard Cave shoot-em-ups such as DoDonPachi or Ketsui, you are awarded with a second loop that's even harder, followed by a True Final Boss that makes that look like a cakewalk, or with very exceptional play, an Ura second loop which is even harder than the normal second loop.
Radiant Silvergun has Saturn Mode, which, given the superior hardware of the Saturn (as opposed to the ST-V original), adds in voice-acting, cutscenes, extra bosses and what have you. Relevant to the trope, though, is how it saves the levels of your weapons - Silvergun powers up your weapons depending on how many points you rack up with them, and higher levels are far more powerful - allowing you to start a new game with fully-powered weapons, making the game a bit more of a breeze.
If the player completes Hydorah the surviving space-navy personnel are shown celebrating. Starting a new game thereafter provides the player with shields, doubling his hitpoints from one to two... but starting a new game right away changes the intro. Initially your commander gives an short inspiring speech as your fightercraft leaves the mothership. In a immediately-started new game he is disheveled and can't form an unslured, understandable sentence.
A staple of the Ace Combat series that allows you to keep aircraft and money/credits earned in previous missions when you start the campaign over on the same save state. Since there's no scaling to account for the ability to select late or endgame planes far earlier than normal, Game Breaker potential is almost inevitable. This also unlocks Free Mission(s) — fly any mission in the game, any difficulty (that you unlocked), and if you're looking for that elusive "S" Rank or an Ace kill, it counts towards your campaign unlockables! (You only have to play the Campaign to buy/sell those unlockables, and to get the money for that.)
The Naval Ops (AKA Warship Gunner) series carries over created ship Designs, Blueprints (templates), R&D, Parts, and Funds whenever you clear the final mission, save your data, and then choose Continue instead of New Game at the main menu. All playthroughs after the first use a more difficult "Enemy Deployment 2" version of each mission, but in Training you can select which enemy deployment you wish to play against.
Harvest Moon: Tree of Tranquility lets your child grow up and leave to start a new farm on another island exactly identical to yours. Your child starts with the cash you have plus a 10k bonus, level 3 skill in all tools, and most portable goods (like furniture), but not livestock or the buildings themselves.
Animal Parade has one as well, but you don't start over as your child (genetics would get hairy); instead your child goes and meets a new rancher on a new, identical island. But cash and items don't carry over; you start with full stamina, Goddess-level watering can and hoe, and one singular item from your old game.
And the one singular item is only if you gave your child a gift before they left. If you didn't give them one, (you can probably read that as you didn't know you could) then there's no real link to the first game at all.
In the iOS/Android game Game Dev Story, after completing a 20-year campaign, you can start a new game with the same levels for the genres and game types that you had with your previous game, as well as points accrued toward game direction. Everything else (staff experience levels, consoles, etc.) has to be unlocked all over again, though, since you're starting over as a year-one studio.
Upon completion of Final Fantasy Crystal Chronicles: My Life as a King, you're given the choice to start a new game with information from your game clear file on one of three difficulty levels - Normal, Hard, or Very Hard. Whenever you build new houses in your new kingdom, many of the adventurers from your old game will move into them, starting over at level one, but retaining all of their equipment, skills, and behavior from their previous adventures.
Stealth Based Game
In Metal Gear Solid, after completing the game, depending on which of the two ending story paths you chose, you could start over with one of two super-items: A headband that grants unlimited ammo, or an optical camouflage suit that grants invisibility. Get both endings, and you can play through the game the third time in a tuxedo, plus keep both special items (and, for some reason, the color scheme on the Cyborg Ninja's armor will be different). The sequels only ramp this up further, often with even tougher requirements:
Metal Gear Solid 2 Sons Of Liberty starts you with a digital camera on the New Game Plus; similar to the camera Snake is given in the Tanker chapter, but allowing you to save the images to your memory card instead. It also features, in addition to the stealth camo and bandana from the last game, a series of wigs that Raiden can wear to gain the same effects as the above, plus enhancing their Super Not Drowning Skills or grip while hanging, aquired by holding up a certain number of guards and getting their dogtags. And, finally, in the Substance rerelease, beating the game once, then beating it new game plus once gives both player characters sunglasses.
Metal Gear Solid 3: Snake Eater gives you the Patriot rifle, which has an infinite ammo supply because the feeding mechanism is shaped like the infinity symbol, after you clear your first playthrough. It also features alternate conditions for getting some of the unlockables, such as aquiring one of every edible item, catching and keeping the Tsuchinoko, or shooting every toy frog in the game; extremely helpful as the only other way to unlock these are beating the game with no alerts, no deaths, no kills, under five hours, etc. One of the new unlockable items is the extremely gamebreaking EZ Gun, a tranquilizer pistol with a laser sight, a supressor that never runs out, and somehow bumps the player's camo index all the way up to 80% whenever it's equipped. You can also start a new game with Ocelot's Single Action Army, assuming you picked the right gun in the duel at the very end.
Finally, in Metal Gear Solid 4: Guns of the Patriots, as long as you load the save file for a cleared game you can use any item you've unlocked, although the stealth camo and infinite ammo headband can also be purchased (for 5 million DP each, 4 million on Sundays/Wednesdays, or 2.5 million in Act 5), and the Patriot requires that the player achieve the Big Boss Emblem (that or a password). Killing all the bosses nonlethally and collecting dolls after their fights also awards the player with a weapon powered by sunlight. There's also a host of new ammo and grenade types, different camouflage patterns, and even a series of masks with special effects.
The Hitman games from Silent Assassin and onwards had a variant where you could revisit missions that you have already beaten but are able to bring along weapons that you have collected from later missions. This not only opens up some new avenues for performing your hits but also is also one of the few ways to collect all of the weapons in Silent Assassin as you keep what you have on you when completing the mission, but can only carry one rifle (or certain melee weapons) at a time.
Blood Money also keeps your upgrades if you revisit previous missions, allowing for things such as tearing through the tutorial and other early missions with dual silenced Silverballers.
Every game from Silent Hill series. In another playthrough you can obtain extra weapons and different endings, which weren't possible to get in the first play.
Parasite Eve 2 had you keep a percentage of your BP and EXP each playthrough so you could get the good items and spells from the start.
Parasite Eve lets you keep your best weapon and armor, and all items kept in storage. The Bonus Dungeon is not accessible in the first playthrough; it only appears in EX Mode.
Interestingly, Parasite Eve only lets you keep the best weapon and armor if you named them at the end of the game. For those who didn't, it was quite the shock to lose the weapon you've spent the entire game building up.
Although all weapons, armors, and items that Wayne held onto you would also be carried over in your next new game plus the next time you spoke to him. This was practically one of the few ways to power up your equipment if you were planning to tackle the Chrysler Building.
Most Resident Evil games allow you to start with an extremely powerful gun once you unlock it, usually by clearing the game really fast, with a very high score. And of course, you get a closet that fills up with spiffy new outfits.
Resident Evil 2 had two playable characters; Claire and Leon. Each had two different scenarios, all stemming from which way the car at the start crashes. To begin with you could just play Claire A or Leon A, both of which show the character ending up on the left hand side of the crash. Beating Claire A got you Leon B, while beating Leon A got you Claire B, showing what the other character got up to during whatever A game you just beat. The game was also affected by what decisions you took in your A game, for instance, picking up a pouch that allowed for extra items to be held would mean it's not there in the subsequent B game. The B games had different bosses, and a few more enemies here and there. Doing well in these and getting a top rank would unlock some new weapons to be found in chests, each with unlimited ammo.
Furthermore, completing all of these (beating the game four times), unlocked The Fourth Survivor mode, a minigame where you guided an Umbrella Agent named Hunk through the Raccoon City Precinct to the helipad on the roof. This isn't so much a New Game Plus, but rather a new mode, recycling old level data, but it's worth noting that doing well in this unlocked a new character, Tofu (which is literally a giant block of Tofu), who serves as something of a Hard Mode for this already hard bonus, as while Hunk is armed with several guns, Tofu just gets a combat knife and a couple of herbs.
Resident Evil 4 allowed weapons, items, ammunition, and current maximum life bar length to be, upon finishing the game, carried over to a new game. This process could be repeated ad nauseum, and could result in the player's inventory being literally filled with hundreds of rounds of ammunition and dozens of healing items from multiple play-throughs.
It's a lot of fun going through on your third or fourth playthrough and fighting bosses that tore your soul apart the first time...but with a rocket launcher that never runs out of rockets.
Resident Evil (GameCube): Beating the game with both characters (using the Once Again option for the second character) would unlock 'One Dangerous Zombie' mode. Beating that would in turn unlock 'Invisible Enemy' mode.
Dead Rising lets you start a new game at any point, and Frank West keeps his level, skills learned, and whatever pictures were in his camera. You have to re-collect items, and you can't earn unlockables if you do this before getting an ending.
This is actually a requirement to complete the game fully, as you cannot complete all the tasks in one run through. Additionally, beating the game the first time through is extremely difficult, because Frank's item capacity, speed, and special moves will be fairly low.
Although difficult, it's far from impossible to complete the game the first time through. The key difference is that Frank will not be able to rescue most of the survivors the first time through, and it's in fact extremely difficult to rescue all of the survivors even with a maxed out level.
It is in fact completely impossible to rescue all the survivors no matter what you do. Following the plot to Ending A will kill some, and not following the plot won't allow you to get them all in the first place. The fact that their AI is utterly horrible and actually getting more than 2 or 3 of them into the safe room at the same time is an excercize in frustration.
Dead Rising 2's New Game Plus is similar to the first game's, as the only things that carry over is money, level, combo cards, and keys.
killer7 gives players the chance to revisit any and all previous levels after beating them, with all the character upgrades the player has gained until that point. However, at the end of the game the player can no longer generate serum for character upgrades, so their levels are pretty much locked in place for individual level replays. Beating the game, however, unlocks killer8 mode, which lets you start over with an even higher difficulty level than before, as well as a new selectable player character, and beating that unlocks hopper7 mode, which allows you to play the first level with most of the enemies swapped with giant grasshoppers.
Dead Space goes so far as to have "Round 1" marked on the save slot during your first playthrough, as well as awarding some nice bonuses for game completion that can be used in round 2. And believe us, ripping through the game's early enemies with a fully upgraded Line Gun is incredibly satisfying.
Dead Space 2 lets you change the difficulty when you start your next round, allowing you to jump into Zealot difficulty with a full arsenal and a store full of extra ammo. Sadly, the bonuses for completing the game don't carry over.
After beating Fatal Frame in Normal Mode and getting the canon ending you unlock Hard mode with a bonus ending. And you can reload all of your cleared games, including the Easy Mode ones. When you reload a cleared game you get to keep ALL power-ups, documents, items, and other stuff you collected in the previous game. And there is the bonus costumes....
Third Person Shooter
In both of the Max Payne games, completing on the game on the first difficulty level unlocks the second difficulty level, and so on and so forth.
Plants vs. Zombies lets you run through the game again, once you beat Zomboss for the first time, keeping all the seeds you've collected so far - but with the price that Crazy Dave now picks three of your seeds every time, on the second play through.
Also, subsequent playthroughs send more waves of zombies after you and a second playthrough is the only way to find the secret zombie and get the Cryptozombologist achievement.
Turn Based Strategy
Some Nippon Ichi games, such as Disgaea and Makai Kingdom, have "New Game Plus" options that allow players to keep all of the characters they've created up to that point, along with all of the awesome weapons they've collected. Almost a necessity, as these games are always rife with extra dungeons, bonus bosses and multiple endings.
Starting a new game via clear data also makes Pelleas and Lehran recruitable. This leads to new dialogue, but the units themselves are far from spectacular.
Additionally, playing a second playthrough extends the backstory with the addition of new scenes and dialogues.
In Path of Radiance, from the second playthrough onwards, certain characters gain bands that increase the growth rates of one or two stats by a small amount. You can also set a different method for levelling up the characters, but it doesn't end up much different from the normal, random method. Playthroughs after that can unlock special characters to play in some trial maps.
In Tsukihime, beating the game once is required to unlock the "Far Side of the Moon" routes. To clarify, before you can access Akiha, Hisui, and Kohaku's routes, which focus on the Tohno family history ("Far Side"), you first have to work your way through the Exposition of Nasuverse-stylevampirism in the Arcueid and Ciel's storylines ("Near Side of the Moon").
In another Nasuverse VN, Fate/stay night, you have to finish the Fate route to unlock the Unlimited Blade Works route, and you have to complete UBW to unlock the Heaven's Feel route. Also, to unlock the final Tiger Dojo segment, you must discover all the Multiple Endings (including all the Bad ones where you die) from all routes.
In Nine Hours Nine Persons Nine Doors, starting a New Game Plus is required to reach the true ending. For plot reasons. Turns out, not only are you starting a New Game Plus, but Akane is too.
Wide Open Sandbox
Borderlands allows you to complete a second playthrough with the same levels, equipment, and stats, with many more enemies and all levels ramped up. The fun part is that you can switch between the two playthroughs at any time, meaning that by the end of the second playthrough, you can kill the toughest enemies in the first with a pistol shot to the foot.
You'll also be much more likely to face Badass (or in this case, Badmutha) versions of enemies in Playthrough 2, as well as facing more (and tougher) enemies.
After playthrough two is completed, the game is ramped up a second time giving access to better quality rewards but without adding another playthrough option or resetting the quests already completed, which makes all those double-powered up versions of one-time only quest rewards lost forever (better save those side quests until after the end fight).
Borderlands 2 has the same thing (dubbed "True Vault Hunter Mode"). A DLC was later released for Ultimate Vault Hunter Mode, which as well as featuring the standard ramped-up difficulty and increased drop-rate of better loot also features Legendary Loot Midgets, who are likely to drop Legendaries and Pearlescent items.
Way of the Samurai allows you to start a new game with your old sword, complete with all of your upgrades and learned moves. Also, any moves that you have Alpha Blocked in the previous playthrough will be auto-blocked, making some of the early fights much, much easier, allowing you to acquire the main characters' unique swords. However, you can still break your sword if you stress it too much and the upgraded sword will be Lost Forever if you die, so one should still be careful.
Prototype has a New Game+ mode. You can restart the story on any difficulty with all of your powers, tokens, side mission medals, and Web targets. You don't, however, get vehicle piloting skills until the relevant story mission.
Prototype 2 has pretty much the same New Game+ features as its predecessor.
In the New Game+ of Batman Arkham City, any riddler trophies/riddles solved will be shared between both regular and New Game+. Also any upgrades will be carried over between the two modes. However, enemy configurations will be changed (meaning that you'll see tougher enemies sooner rather than later), enemies themselves get tougher and more aggressive. Also, you get no counter indicator. In other words, New Game+ is Nintendo Hard when compared to the regular game. Not to mention this New Game Plus can only be used on normal and hard difficulty, you can only have a single New Game+ per save file and can't start it over again and to get 100% Completion, you need to finish all other sidequests in both the main file and the New Game+.
Driver San Francisco features one after completing the main story which allows you to fully explore the entire city with your highest level of shift and abilities and carried over your vehicles, garages, willpower points, ability upgrades, etc.
The Incredible Hulk: Ultimate Destruction has a New Game+ option. All your learned abilities carry over, as do unlocked costumes. Playing through again with the Joe Fixit skin (which makes the Hulk quip and snark constantly, but you probably won't unlock it until after the story) has the bonus of Joe/Hulk making comments during boss fights and such.