Finishing Gungrave: Overdose with all three protagonists will allow you to turn on the option for "Alternate Character". Rocketbilly Redcadillac gets a Garino Corsione skin and Juji Kabane gets a Bunji Kugashira skin. Hilarious in that playing the game with these equipped has the characters yelling the lines they used during their respective boss battles when attacking. And as for the original hero Beyond the Grave, he will wear his badass purple cowboy suit (complete with his Nice Hat) from the original game.
The Nightmare Before Christmas Oogies Revenge gives you extra outfits for Jack, depending on your overall completion rank, that do not alter his abilities or appear in most cutscenes. However, in Easy Mode, for collecting all the trophies in the game you no longer need red souls to use the fire abilities in his Pumpkin King costume.
Beating each difficulty level of Drakengard 2 earns accessories that lets you change Nowe, Eris and Urick's outfits to Knight of the Seal, Goddess, and Helmetless, respectively. That's it. Another one changes Urick's model for a generic NPC. Since they have to be equipped, replacing gear with mechanical benefits, they're useless.
The Namco arcade game Dragon Buster features a Crown item that changes the outfit wore by Princess Celia every time she is rescued by the player. She goes from her default royal gown to a miniskirt and tank top and then to a bikini. If the player picks the scepter and crown at the same time, she will dress like a Playboy Bunny by the fourth time she is rescued.
Sine Mora awards extra plane paintjobs for various feats. You can also unlock 'art filters', which change overall appearance such as colour saturation, brightness, and so on.
The Tekken spin off Death By Degrees rewards you with new outfits for Nina. Don't worry, you do get actual weapons and equipment as well along the way.
The Anniversary and Legend versions of Tomb Raider had various outfits for players who completed the time trials. Anniversary's was mostly a Shout Out to past games, including one where you get to play as a remade version of Lara's old polygonal model from the very first game, pointy boobs and all.
Beating The Legend of Zelda: The Wind Waker unlocks the option to have Link keep the outfit he wears in the beginning of the game, rather than switching to his iconic green tunic early on.
And you also get to start with the upgraded camera, making the Nintendo Gallery sub-game far easier. Also, any figurines you had made in the first playthrough are carried over.
In the Game Boy Color re-make of Link's Awakening, your reward for beating the optional Color Dungeon is a choice of either Red Clothes (boosts attack) or Blue Clothes (boosts defense). You can return to the dungeon anytime to swap colors (but you can never get the original Green Clothes back...).
Spirit Tracks has a stamp book subquest that, among other rewards, unlocks the conductor's uniform you wore at the beginning of the game. The shield from Phantom Hourglass is also unlockable with 10 stamps. But it can't be eaten by Like Likes, so it's a bit more practical than the regular shield.
For a non-purely-cosmetic example, in Majora's Mask it was possible at the end of the game to unlock a special mask that would serve as a fourth transformation, though only against bosses. It was called the Fierce DeityMask, and it was as cool and overpowered as it sounds.
Okami rewards players by giving them alternate canine forms for Amaterasu, which are mostly cosmetic. Just about any dog or wolf seen in the game is usable, as well as some alternate paint schemes for Ammy. The most interesting of these is, perhaps, her 'Realistic 3D' skin, which makes Amaterasu stand out like a sore thumb in a world that looks like a Japanese painting come to life.
Bully features a wide number of in game tasks and errands whose only reward is clothes, the majority of which don't do anything. One errand early requires you to find pills for a homeless man; your reward for completion is a cool looking but useless black cowboy hat. Lockers that can be broken into in the school frequently hide clothing items. Taking all the pictures for the school yearbook unlocks the Black Ninja costume, which causes prefects to not notice certain minor rules infractions when worn. Getting all the clothing items in the game is required for 100% completion. The missions and classes added in Bully: Scholarship Edition for the Wii and X-Box 360 mostly just reward you with new clothing items.
Beating Iji on Extreme mode unlocks an alternate costume.
Katamari Damacy has hidden presents in most levels that give you different pieces of clothing to wear such as a chef hat or a scarf. You can also find the Prince's cousins, who all look different, and play as them. Also, some of the presents will look different on some of the cousins.
After beating story mode of Batman Arkham Asylum, an armored batsuit is available to wear in Challenge Mode. After beating the story mode in Batman Arkham City, you can use Batman's alternate models, including 1970s Batman, Sinestro Batman, Batman Beyond Batman, and others.
Beating all the missions for a character in Sonic Adventure 2 rewards you with alternate costumes for that character to use in 2P Battle. These costumes change something about the character's special moves (which they get from collecting rings), i.e. Shadow gets a five-second Chaos Control for every 10 rings he gets, and Tails gets a massive speed boost but has all of his moves removed.
The Marvel Ultimate Alliance games (and its spiritual predecessors, the X-Men Legends games) reward characters for doing certain achievements (like defeating a set amount of enemies) with bonus costumes. Counting standard costumes, in the first game, every hero (except Moon Knight) has four costumes, but sadly, in the second game, there are only two costumes per hero.
Subverted in that each costume grants different bonuses.
In Strong Bad's Cool Game For Attractive People, there's a photo booth that lets you try on various costume items you find throughout the game, but you can only wear the costume items while in the booth until you beat the game.
In Kings Quest VI, after Alexander helps the Beast by finding him a hot servant chick who will love him, he gets two rewards: a silver-lined magic mirror which reflects the truth to the viewer, and... Beauty's old clothes. Granted, you need them to beat the game (whichever of the Multiple Endings you choose), but still. Magic mirror vs. rags. Let down.
Chibi-Robo!! has a number of different costumes Chibi can unlock by doing the sidequests (and in one case dying enough). But they all do different things, and poses. The Pajamas allow you to switch between day & night. The Ghost Costume scares people. Frog & Tao costumes let you talk to... Frogs & Tao. And then there's the Super Chibi-Robo "suit" (it's a single medal with "s" on it pinned on the chest as well as making chibi slightly more shiny), which you can get for reaching the top happiness rank (It's impossible to get top happiness regularly, you must beat the game to get the top happiness rank otherwise you will be suck at number 2.)
Endless Ocean likes to reward your hard work completing quests by giving you new gear. None of this has any effect on gameplay; the actual upgrades you have to buy. Oddly, the first game manages to send you a wetsuit through e-mail at one point.
God Hand allows you to change your outfit to the ones used by the Devil Hand, Ryu from Street Fighter and the Camp Gay duo Q & A. You can also give Olivia a bunny outfit.
The Warriors has an extra difficulty called Unleash the Fury if you get 100% completion on Hard. Unleash the Fury is the hardest difficulty level and all of your Warriors are dressed up as the Baseball Furies. This leads to a hilarious and somewhat disturbing encounter on level 16 where you'd normally meet the Baseball Furies and instead, you fight mass armies of Warrior clones!
In the home versions of Tekken 5 and 6, the brawler side-games allow you to win costume elements that you'd normally have to dish out a lot of fight money for. In 5, it was just the 500,000G options for the non-time-release characters, and you had to nab hard-to-reach Devil sigils after clearing the game the first time. In 6, felled enemies and destroyed crates have a chance of releasing a treasure chest that unlocks a random non-hair-related item for either your active character or your AI partner (i.e. Alisa or Raven). It's possible to unlock multiples of the same item, down to the same color scheme, since a random quality for Scenario Campaign is appended when the item is gained. In any case, don't be surprised to get five or six items in a single area, even without equipping something that boosts the item drop rate.
Final Fight One, a Game Boy Advance port of the original Final Fight, allows the player to play as Cody and Guy in their Street Fighter Alpha outfits after defeating a certain amount of enemies. The Alpha versions of Cody and Guy used the same sprites they had in the Alpha, but otherwise they fight identically to their original counterparts.
Based on a Movie/TV Show
The Wii adaptations of "Jeopardy" and "Wheel of Fortune" offer clothes as a reward for winning mini-games.
Driving and Racing Games
Excite Truck gives you another skin for each truck if you race with it 10 times or get an S rank three times.
Mario Kart Wii has Mii Outfit A and B, which changes the looks of your Mii when you race as one. Outfit A gives you a jumpsuit look while Outfit B gives you the Mario shirt and overalls combo if the Mii is male, or a dress in the style of Princess Peach if the Mii is female.
Need for Speed Underground features a large amount of possible car customization, ranging from performance upgrades (which affect your gameplay) and cosmetic changes (which don't do shit). The way one earns these upgrades is through winning races. The only problem is that all you earn for a large portion of the beginning of the game is decals.
Underground 2 sort of fixed it: you need visual upgrades to increase your street cool rating and get more races.
In Most Wanted the only thing visual upgrades do is enable you to tweak your aerodynamics, which has very little effect offline (and online everyone uses the untuneable bonus car anyway) and you can do that whether you get a bodykit, a huge spoiler wing or a tiny little spoiler that looks like it came as a factory option with the Sport Edition of your car. Also, painting your car reduces police attention... making it harder to complete the police challenges until you vandalize the place again. And they still cost money. Enough to add up to a new car later on. So nobody does it.
Pro Street takes the (ahem) realistic route of having almost every visual upgrade make a performance difference, but often fails to tell you what the difference really is. Bodykits reduce weight... or maybe they sometimes increase weight, it seems to depend on the car. Then you get to change the shape of your bodykit parts, which according to the ingame graphs increases downforce AND reduces drag. This can't be right, but nobody knows what it really does. And again, offline it doesn't matter and online there is a much better alternative for fiddling with aerodynamics: sideswiping the other bastard into a wall so he loses 10 seconds and you win regardless.
GRID is a racing semi-simulation, so you cannot visually tune your car and your visual options are limited to car colours and sponsor stickers. However, do not get carried away with changing your paint until it is juuuust right. Due to a mysterious bug/feature, changing your paint or washing your car causes its durability to go down until you make it dirty again! So much for simulation.
Open world offroad racing game FUEL relied too much on player vanity. The entire point of the open world seems to be to make the player go out and track down car wrecks which resulted in new clothes and vehicle paintjobs. However, the world is gigantic, to the tune of tens of thousands of kilometers, and driving for half an hour to find some crashed motorbike with a slightly different pattern on the fuel tank was considered a waste of time by most players. So the open world was considered useless and the game died a quick death on the market.
Burnout Paradise awards you with new cars as you progress through the game. When you finally complete every single race, you get... gold paint.
Test Drive: Unlimited has an entire class of missions which reward you solely with clothing vouchers.
SkyDrift awards extra plane paintjobs for completing various challenges, such as winning a certain number of online matches with that plane.
The Whyt mini-games in the DS remake of Final Fantasy IV reward you with new outfits for Whyt if you achieve 9,999 points on a particular game. Which outfit you get is dependent on whose game you beat (e.g. a Paladin outfit if you beat Cecil's game, etc).
All three Xenosaga games give you alternate costumes. Episode III in particular gave you access to Shion and KOS-MOS's Episode I outfits. KOS-MOS is Bad Ass no matter what her appearance, so her alternate costume is simply there for the nostalgia factor.
Xenogears makes a minor plot point out of Alice's wedding dress. Alice, Fei's extremely Unlucky Childhood Friend dies early in the game on the eve of her wedding. When you're forced to fight her little brother Dan in a tournament you can choose to let him beat you, at which point he gives you the dress to remind Fei that it's his fault Alice is dead. Hilariously though, the dress is equippable and has some rather nice stats to it.
Xenoblade expands the proud tradition by giving everything you can equip its own appearance, but still offers kit with particularly unique appearances as quest rewards. Yes, this includes fanservice-laden swimming costumes... that tend to have excellent dodge bonuses and multiple ether slots despite their abysmal defense boosts, making them actually viable on some characters.
Tales Of Symphonia rewards you on many sidequests with titles that have an attached costume. However, they're usually not good to wear in combat because the equipped title also impacts stat growth.
Lloyd: (while wearing swimming trunks, goggles with snorkel, flippers, and two swords) *ducks into a room* Whew! That was close!
Yuan: And just who the hell are you?
There's also a minor glitch involving the clothes-changing titles: If you change Colette's outfit before visiting the Fire Seal (the third major dungeon), she will hover around the battlefield as if she already had her wings.
Many other Tales games also have costume titles, and most of them do not tie stat growth to titles. This makes the costumes much safer to use in battle.
Paper Mario: The Thousand-Year Door rewarded players that completed certain side quests by giving them badges that change Mario's colors to Luigi, Wario, or Waluigi if you combine the Wario and Luigi badges. While these are purely just for looks, one side quest actually requires the L Emblem badge to make someone think Mario is really Luigi since she's a huge fan of Luigi. After the quest, the real Luigi arrives, and gets chased off as an impostor.
Final Fantasy X-2 actually revolves the whole gameplay around dresspheres, which are clothes with special powers that grants the party different attacks and stats. Getting new dresspheres is a reward worth getting and is a requirement, thus justifying the trope.
Taken further back with the whole "Job" system of the older games, with each job coming with the requisite clothing.
Wild Arms 5 contains special clothes that alter characters' appearances... they vary between being powerful and useless. Most of them are only obtainable by spending special coins rather than normal ones.
Dragon Quest VIII has some armor that changes appearance; Jessica in particular gets to be dolled up in various ways to show off her obvious assets. Her best and worst outfits both change her character model.
Shadow Hearts Covenant had alternate costumes for the three female party members, as rewards for endgame sidequests. Anastasia had an orange kimono, Lucia had a bridal dress, and Karin had... this so-called "Dating Outfit"◊. There were also two accessories in both this and the first Shadow Hearts, Black Silk Panties and Cotton Underpants, that would in fact give these characters said colored underwear.
Persona 3FES has several sets of party-member outfits, ranging from summer clothes to French maid costumes, that are mostly earned by completing Elizabeth's requests. All of them have decent defense stats, and, as Junpei puts it when you tell him to equip one of the outfits...
Junpei: "Dude, you want me to run around Tartarus in my swimming trunks? ...that's AWESOME!"
Unfortunately the girls don't share this sentiment and just think you're abusing your power as leader.
This also carries over to the Updated Rerelease of the Updated Rerelease, Portable. Equipping the girls with the embarrassing outfits changes from a "you're enjoying this, aren't you" bite-back to a more subdued "you think this is funny, don't you"-style of dialogue. The guys, meanwhile, get distinctly flustered if the protagonist equips them in tuxedos or herself in her bikini or maid outfit, and downright appalled if she dons the "Battle Panties."
In Dark Chronicle, completing challenge objectives on a floor of a dungeon will reward you with medals. These challenges range from only damaging enemies with a specific weapon type, not healing, a time attack goal, performing well in the Spheda/fishing mini-games, etc. Take these to the Mayor of Palm Brinks after recruiting him, and you can spend them on specialty clothing that isn't available any other way (save for some of the boots, which can be invented). The clothing itself is for nothing more than aesthetic appeal. These all show up during cutscenes, which can turn heartfelt moments and epic sword fights alike into a bit of a Narm if Monica is in a StripperificFur Bikini and Max is a clown.
One of the bonuses added to the PS3 version of Eternal Sonata was alternate costumes for Polka, Allegretto and Beat, the three characters that you can control in the field at various points in the game. Polka gets two extra costumes, while Beat and Allegretto both get one.
The Fossil Fighters games tend to reward you with masks the main characters can wear for completing certain sidequests. In the first game, these are mostly cosmetic, and just change the the sound effect of your walking. In the sequel, however, some of the masks have effects, like making it so you can only find fossils of certain elements, or certain fossil body parts. (Plenty of cosmetic masks do exist, however.) The sequel also sometimes rewards you with "icons" that change what sprite represents you in battle.
Played straight in Mortal Kombat Armageddon's Konquest mode. Many of the chests just contain...skins for your paper doll fighter. There are also plot-important clothes in the game.
Also the 2011 Mortal Kombat game. By beating Arcade Mode, you get alternate clothes for your character. Some of them are plot related, such as human versions of Cyrax and Sektor. Completing the Challenge Tower will reward you with a Stripperific costume for Mileena.
In Mortal Kombat Deadly Alliance, all the characters except Blaze and Mokap have unlockable alternate costumes that you can purchase in The Crypt (where all unlockable features are obtained).
In the Dead or Alive series, each character has multitudes of outfits, which form the main reward for beating their story mode, a new outfit coming for beating each difficulty several times. Girls do tend to get about twice as many to unlock as their male costars, but only useabout the same amount of material.
Dissidia has one (two in Duodecim) unlockable costume(s) per character. They can be bought for Player Points in the PP catalog, and they aren't very cheap. Also, there are DLC costumes for some characters.
Magical Girl Lyrical Nanoha As Portable: The Gears of Destiny foes this for all the returning characters of the first game and Yuuno. Civvies are unlocked by beating Arcade mode without losing. Namco Shout Out outfits are unlocked by beating Time Attack Mode under 300 seconds. Swimsuits for non-Material characters are unlocked by beating Aracade, Time Attack, and getting 10 wins in Survival. Everything else is limited release DLC.
First Person Shooter
Halo 3 gives you different pieces of armor for beating the game on normal, heroic and legendary, getting achievements, and getting all the skulls. The armor pieces have no effect on gameplay, and are only available in competitive multiplayer.
The ultimate bragging rights armor for Halo 3 is Recon. Originally, recon was only attainable through impressing Bungie somehow (for instance, the first person to post on YouTube his character being killed by a traffic cone received it), and only a small amount were given out. With the September 2008 update to Halo 3, a new series of "Vidmaster" Achievements were added. Getting the four vidmaster achievements in Halo 3 (and three more in Halo: ODST) unlocks recon armor, though three of the achievements are very hard to get.
Halo: Reach expands the customizable armor system significantly, and lets you use your custom character in every game mode. Armor is purchased with "credits" that you can earn by doing just about anything in the game. (The Recon helmet from Halo3 is awarded for picking the game up on launch day.) As in 3, the armor has no effect on gameplay.
It should be noted that Recon can be unlocked (in Reach) via. standard promotions without needing the code. But, the code does make the process a little faster.
However, the helmet unlocked on Day 1 is noticeably different than the one attained through gameplay, so the Recon helmet from Da1 purchases are still more "special".
Whenever you enter Prestige Mode in Call of Duty 4 (resetting your level to 1 and re-locking all the weapons, mods, perks, etc. you unlocked by leveling up, starting a new game in online play), you get a new type of badge to show your elite status. Additionally, completing all of the Marksman and Expert challenges for a given weapon unlocks a gold version of that weapon that, other than the gold finish, is no different from the normal version (the exception being the Desert Eagle; the Gold Desert Eagle is unlocked at level 55, the maximum level and the level at which Prestige Mode is unlocked).
Team Fortress 2 has hats that, in addition to being buyable or given away as promo with purchases of certain games, randomly drop like other items but at a much lower rate and can be crafted randomly from a large number of weapons or two hats, unless they're player submitted ones in a set that can be specifically crafted with an even larger number of weapons including one from that same item set. Neither of which is available to people playing the game that have not paid anything for it.
Brink does this to the Nth degree, to the point that specific enemy and friendly players are recognizable immediately on first glance.
Hack and Slash
No More Heroes gives you an extra T-shirt for completing the game plus unlocks more for you to buy if you play again.
Inverted in the sequel. Completing all the revenge missions allows you to not wear a jacket.
God Of War games give you the option of humiliating either Kratos or his enemies (depending on your viewpoint) by having him wear various crazycostumes, some of them being groanworthy puns of the games title, although at least the costumes themselves give you various gameplay changes. Examples involve Cod Of War (fish suit), Chef Of War (self-explanatory), Bubbles (surfer), Tycoonus (businessman), Dairy Bastard (cow suit) and a version of the outfit worn by the first game's Big Bad.
In Bujingai, you can unlock an outfit for the main character that makes him look like the *cough* actor he was modeled on. Given that the actor is Gackt, this makes for a cringingly strange look as your leather-pants-and-tight-shirt hero fights ancient Chinese technicolor baddies.
In Devil May Cry 3, the player is rewarded for completing the game with... less clothes. The option to play Dante shirtless for the whole game is unlocked.
Then there was the legendary dark knight costume, complete with monocle and demonic shadow, from the first game...but you also got infinite devil trigger, which was a damn good reward.
Upon completion of the main game, Samanosuke in Onimusha is granted a giant panda suit, with such features as a head that flips back and a large flower in place of his Ogre Gauntlet. Completing the game with an S ranking will unlock a less hilarious (but still cute) alternate costume for his ninja sidekick Kaede as well.
In Dawn of Dreams, some of your characters can get Street Fighter costumes! Tenkai on the other hand, can get the rockin' costume worn by Sieg, the main character of Chaos Legion.
Some of the very expensive items in Bayonetta are just alternate clothes which do nothing but increase (or, sometimes, decrease) the fanservice.
Massively Multiplayer Online RPG
City of Heroes and City of Villains rewards a wide variety of successes, ranging from completing the original Task Forces to slaughtering a lot of Rikti with new clothes and different looks for weapons. These are considered the best rewards.
This is mainly because, unlike a certain other popular MMO clothes have nothing to do with power levels and abilities and are on the rare side in-game. You do start with an enormous amount of costume pieces to choose from, so if you see someone running around with a cape or sword design you've never seen before, you just know for sure that he's accomplished something impressive.
Most of the quests in Age Of Conan give items of clothing as a reward. In fairness, they do all grant bonuses to the character but it seems to be somewhat off-kilter for you to walk the length and breadth of a warzone gathering items to help put the dead to rest and then be rewarded with a blue leather gladiator skirt.
While plenty of quests in World of Warcraft give armor as rewards, there are some that award clothing items that have no practical in-game value. Most of these are effectively Cosmetic Awards, although you may also get experience and/or gold alongside. There is even a quest that involves going back in time just so you can get a nice hat. Ahem, Nice Hat.
Some players take this a step further and deliberately hoard clothing items so they can roleplay or just show off. Furthering this, many of the holiday events in the game have special currencies that can be gathered and traded for items of no practical value, including clothing (and some of these are required for in-game achievements).
The tailoring profession also has a small subcategory devoted to sewing shirts. And, as of Cataclysm, a gorgeous dress with material requirements on the level of epic quality armor.
Getting your reputation to Exalted with any of the many factions generally has little long-term advantages (apart from cheaper repairs), but many offer a tabard, pet, mount or even a title for those that go through the effort.
In Wrath of the Lich King, the second available Legendary weapon was an axe called Shadowmourne and getting it involved completing a marathon of quests that required killing certain bosses under special conditions, collecting 40 macguffins - each boss had a chance exactly one - and so on. The very first time a player kills the Lich King after attaining Shadowmourne, he drops a one-time-per-Shadowmourne Easter Egg bonus box of loot that contains entirely cosmetic or novelty items, including a tabard that shimmers and glows on use.
In Cataclysm they added Transmorgrification, which allows you to change the appearance of armor and weapons to look like a different kind of armour/weapon without changing the stats of the original item in question. The only drawback to this was that weapons had to be the same type (No making a Hammer look like Frostmorne for example) and you had the have the item that you wanted to copy the appearance from in question. However they added plenty of items that did absolutely nothing except look cool for your transmorgifying pleasure.
Challenge Mode dungeons, added in Mists of Pandaria are dungeons with more powerful monsters, altered mechanics, and a system that scales down the power of your equipment to Heroic dungeon gear levels, making it significantly difficult content. Additionally, Challenge Mode runs are timed, and you receive a ranking at the end based on how quickly you were able to complete the dungeons. If you can get a gold ranking in every dungeon, you receive an awesome set of class-specific armor for Transmogrification. Netting bronze and silver medals rewards you with a title and mount, respectively.
The different sets of lvl 20 (the max) armor in Guild Wars have mostly cosmetic differences from each other, but the hardest to acquire and most expensive items are cool looking armors (some requiring things like beating the campaigns, doing well in challenge missions, or completing the Brutal Bonus Level)
In zOMG!, there are five basic quest rewards: Gold, Null Fragments, Recipes, Charge Orbs, and (rarely) Rings. Rings offer new skills for you to use, and orbs are used to level up. Gold is Gaia's currency, and can be used to purchase game items from other players, or cosmetic items from shops. (Rings aren't sold at shops, and the other game items are Cash Only if you don't earn them in the game). However, Null Fragments and recipes (in addition to most monster drops) are used for Item Crafting, which can be used to make various cosmetic items for your avatar. However, part of the fun of Gaia Online lies in making your character look and act exactly how you want it; recipes are actually highly sought after.
Null Fragments have long since been removed as quest rewards, since they used to be of limited quantity for players, thus meaning that the number of recipes one could make was also limited. The game was changed so that Null Frags could be traded in for orbs or rings as incentive for players to pawn them off, but that option has also been recently removed.
In Kingdom of Loathing, shirts are the most exotic kind of reward. The population in general, being stick figures, aren't aware that they even have a torso, with the exception of those few adventurers who have trained in Torso Awaregness (it's gnomish), and such training is only available on New Game Plus (after at least one ascension.) Only then will adventurers be able to recognize garb that covers anything between the neck and the legs when it appears.
Also Hardcore and Bad Moon ascensions are rewarded with clothing, accessories and weapons. Hardcore ascensions from all classes yields a full Stainless Steel suit, Bad Moon with Brimstone, both valuable as status symbols and for stat bonuses. Not to mention Oxygenarian Hardcore, which rewards you with Plexiglass items.
In Runescape, a lot of random event and seasonal quests give clothes as a reward. For example, the Halloween event gives you a Grim Reaper hood.
Not to mention Skillcapes and Capes of Distinction.
And of course the Completionist cape. it takes 5000+ HOURS OF PLAYING TO GET IT.
Chompy Bird Hunting: "What's that? you killed 4000 birds by luring them one-by-one and killing them with a weak bow? Here's a hat for you!" The hat has absolutely no use outside of proving you killed 4000 birds.
This is the entire point of Final Fantasy XI. Players (usually of Damage-Dealing classes) even go as far as to say Gear > Skill.
The original Myst: Uru has clothing scattered around that you can add to your wardrobe as a reward for exploring, along with a new shirt as one of the rewards for completing the game. The other expansions also feature scattered clothing.
Ragnarok Online has whole quests dedicated to hats that for the most part don't do anything useful.
Both played straight and (slightly) subverted in the MMORPGMabinogi; with many different styles and designs of clothing and accessories available both as purchases in stores, and as drops from bosses and quasi-bosses. All items of clothing have the exact same stats, with the exception of durability. Subverted somewhat in that most of the dropped versions have enchantments which grant some boosts (or reductions) to certain player stats; although the enchants are typically extracted and applied to other equipment. Played straight with others, in that they're different only in having a very rare color combination, or are unavailable in NPC shops.
Played even more straight with limited-duration special-event quests. Rewards are often clothing or accessories which are completely useless for actual gameplay, as they are purely cosmetic with no useful stats or abilities at all, and cannot be repaired, cannot be traded to other players, or both. If they are useful, they are simply rare color variants of commonly available styles as noted above. Made particularly annoying by the fact that many of these quests are either Nintendo Hard, or require excessive amounts of grinding.
Champions Online does this to an absurd level. Killing one thousand of nearly every enemy group in the game will unlock their symbol as a cape option and killing five thousand of an enemy group unlocks a costume piece used in that enemy group's character models.
In MapleStory, you can spend (real-world) money to buy yourself accessories that don't do anything other than look pretty. Worse, most if not all of said items are only temporary, lasting for three real-world months. Do you want permanent stuff? You have to pay double.
In Guild Wars, since armor is pretty generic in terms of functionality, most attempts to get the "special" armor for both yourself and your heroes are basically made for cosmetic reasons, especially in the case of heroes. You do Glint's Challenge, just so Gwen can have a sexier dress to run around in. And you do crazy numbers of Vabbi quests, or you get filthy rich and further inflate the merchant prices of Rubies and Sapphires, just to get Vabbian Armour for yourself. Which, in functionality, is just the same as any maxed end-game armor.
Character stats are altered via Talismans: magic trinkets that have no visual effect on the player model. However, completing certain missions and achievements in the game rewards purely cosmetic clothing items, including Faction uniforms and outfits related to the character's ability build, or 'Deck'.
The only exception is Weapons, which alter both appearance and stats. However, you can purchase a 'Casting Kit' to duplicate an old weapon's appearance, and apply it to a new weapon. This way, you still get the better stats, but keep the cool look!
Dungeons & Dragons Online has Armor Kits that, when equipped... make your armor look a certain way. Regular armor is a half example since there are a number of appearances any given set of armor can look like, but actually do something. Outfits, used by Wizards, are a completely straight example, since they often have no armor bonus, defensive power, or bonus effect until higher levels.
Star Trek Online has two uniforms (both restricted to the Federation) that arguably count: the Vice Admiral overcoat (unlocked by becoming a Vice Admiral, which is currently the highest rank/level reachable) and the Diplomat uniform (unlocked by becoming an Ambassador via the diplomatic commendation xp system). There are plenty of other clothes unlockable, but those are the two that are automatically unlocked if specific requirements are fulfilled (rather than being buyable).
Guild Wars 2 continues the tradition of its predecessor. Your end goal for running through the explorable mode of the dungeons is to acquire a full set of armor that, although spiffy-looking, is not all that statistically different from what you can get from crafting and drops.
The Art Of Theft by Ben "Yahtzee" Croshaw contains new outfits that your character can unlock by accomplishing certain missions or secondary goals. Some of these are merely appearance, but others have significant game effects (making stealth easier or harder, allowing unlimited use of a stun gun.)
Super Mario Sunshine gave you a tropical shirt for beating the game, to go with the sunglasses you unlock earlier. And the sunglasses actually darken the screen a little.
Perhaps among the oldest example is the first Metroid game, where beating the game within a certain amount of time would net you a password which would allow you to play as Samus in a leotard.
An unlockable option in Metroid Prime allows you to play wearing the Fusion Suit from the game of the same title.
And you did have to beat the game in order to unlock it, in addition to having Metroid: Fusion (though not necessarily beating it)
Likewise, Metroid Prime Trilogy has it as an unlockable after beating the game (though with an added "achievement" price).
In Jak 3, after helping to save the world multiple times, Daxter is free to name any reward from the nigh omnipotent Precursors. He asks for pants. God he missed pants. His girlfriend gets a matching pair.
And to top it all off, when the player collects all 600 of the extremely well hidden Precursor Orbs, their ultimate reward is essentially a palette swap on Jak's scarf.
In Banjo-Kazooie: Nuts & Bolts, beating the game will have Banjo wear a tuxedo, while Kazooie settles on a necktie.
The Ratchet & Clank games generally don't reward you directly with new skins. Instead, you accumulate various bits and pieces, such as skill points or titanium bolts. These generally have exactly one use: new skins*
the other set is used for weapon upgrades when they are special bolts or cheats
when skill points]]. That said, Ratchet defeating half the game in a tuxedo is pretty badass.
If you bought and downloaded Quest For Booty, Crack in Time will reward you with a BadassPirate Hat available at the start of the game.
In the Klonoa Wii remake, Klonoa gains three additional outfits upon completion of the game: his original "collar and trousers" outfit, his Klonoa 2 outfit, and his summer wear.
Castlevania 64 rewards you on a second play through with different clothes if you picked up the second Special.
In Spyro the Dragon: A Hero's Tail, collecting certain groups of dragon eggs unlocks the ability to play as Spyro's fellow dragons, Flame and Ember. Although technically different characters, they play exactly the same as Spyro, they just look slightly different.
Later games in the Diner Dash series gives you clothes after each level to dress Flo in.
The rewards for completing levels in the original Rayman: Raving Rabbids alternate between new costumes (including the Elvis Presley look and a bunny suit), music (including very squeaky versions of "Girls Just Wanna Have Fun" and "La Bamba"), and - at one point - a golden pig.
In Professor Layton's London Life, a bonus sprite RPG packaged in with some regions' version of Professor Layton and the Last Specter, fulfilling some of the quests assigned to you by other characters in Little London will earn you articles of clothing your sprite can wear.
Forza Motorsport 4 has two examples. Community Bounty Hunter events have you trying to beat a well-known Forza player's lap time in a specific car by a certain date, and the events vary between easy and Nintendo Hard. If you win the event, you are gifted a car with a unique paint job (though players often sell replicas of the paint job). The other example are the Badges and Titles; avatars and little snippets of text under your name in the pre-game lobby. Some are easy, like getting a perfect "Turn" rating, or owning 10 cars. The harder ones require a lot of time and determination, such as owning 300 cars, or driving 1000 miles in a Toyota Prius
Completing an especially long setlist in Rock Band will earn a band millions of fans, but as far as material gains go, just $20 and a t-shirt.
Rock Band 2 has special outfits - four of them, one for each major genre - which are unlocked by completing the Impossible Instrument Challenges.
Some Dance Dance Revolution games gave your characters new outfits as you unlocked more songs. SuperNova 2 gave all the characters new outfits from their first one, while Hottest Party 2 awarded the dancers with their HP 2 outfit as well as their HP1 outfit.
Hottest Party 3 took this even further, and had 6 different sets of outfits for your Mii character to wear. That's 6 sets of outfits, including a mecha-suit, an astronaut suit, and four regular outfits. With 5 designs of four shirt/pants/skirt/shoes/etc each. All together, that is at least 30 or so outfits you can mix and match.
Guitar Hero 5 has challenges on every gig in Career Mode. The exact list of unlocks for completing said challenges are cheats (which you can actually use to aid in other challenges, oddly enough), Extra Options (most of which seem to be designed to make things harder), Instrument parts (from the sponsor challenges), alternate costumes (for the premade characters), costume parts (for created characters), ONE venue to play in quickplay, and in three or four specific instances of non-celebrity characters (celebrity characters are just unlocked by clearing the marked gig they show up in). Notice how song unlocks aren't in that list. Also note that the platinum challenges are hard and the diamond challenges are borderline impossible without cheats On Expert (don't even try on Hard or below).
Space Channel 5 Part 2 has a bunch of unlockable outfits for Ulala (some of which actually turn her into different characters) as well as items that can replace her microphone.
Dance Central has at least a couple outfits to unlock for each dancer.
In the original Sims Superstar expansion pack, if you achieved a certain amount of fame, you would get a "High Fashion" outfit similar to the ones worn by the famous Sims (the Sims whose last names are "Somebody").
The Pets expansion pack for The Sims 2 featured various collars and fur patterns as unlockable rewards if your pet got a promotion.
If you use the time machine in The Sims 3 one of the random bonuses you can pick up is a set of 'future clothes'. We'll all look like Tron characters in the future, apparently. You can also unlock a caveman outfit as well as medieval dresses for females and armor for males.
In The Sims Medieval, unlocking enough achievements unlocks new clothes and new furniture.
The Ace Combat series does this, the second playthrough of the storyline adds Aces to each map, usually a distance away from the main objective, requiring you to risk failing the mission in order to shoot them down. Once you do, the extra paint scheme for the Ace's fighter type is unlocked.
Also includes Continuity Nods to older games in the series, such as the SU-37s "Yellow Squadron" scheme from Ace Combat 4 in newer games.
The Trope Namer is Animal Crossing (see the Quotes page), where your neighbors will reward you for going on a wild goose chase to find their camera with items (including clothes). They'll also give you clothes for free once in a while.
Create a Mall rewards the player with clothes and accessories for the playable character.
The SSX series of snowboarding games rewards the player with new board skins and outfits for winning events. The outfits are purely cosmetic but the boards do affect gameplay, with different board types geared towards racing or tricks and boards earned later in the game generally having higher stats. This was changed for SSX 3, where the races reward the player with money and stat points which he can then spend on buying new outfits and reskinning or statting up his board, as well as various other treats like concept art and new background music tracks.
Most of the SmackDown vs. Raw games unlock alternate outfits for your wrestlers after you beat Season Mode or Road to WrestleMania mode. Sometimes cheat codes can be used too.
Killing ten bucks with the same weapon in Deer Hunter unlocks the gold version of that weapon, which... is precisely the same, but look at the shiny! Also good for showing off in online matches.
A mainstay in the Metal Gear series since the original Metal Gear Solid. Completing the main story mode twice (with a different ending each time) and then starting a third playthrough will cause Solid Snake to change into a tuxedo when removes his scuba gear after the opening sequence. The Cyborg Ninja will also be outfitted with a recolored exoskeleton when Snake confronts him. Additionally, Snake will have access to Otacon's stealth suit and a different bandanna (that grants him unlimited ammo) depending on the ending the player gets.
In the Integral edition released in Japan (as well in the PC port and in the GameCube's Twin Snakes version), Meryl will be wearing Snake's sneaking suit as well.
After completing the story mode of Metal Gear Solid 2 twice, Snake and Raiden will start wearing sunglasses during every odd playthrough. Snake wears three pairs (an iridescent gold pair, a black pair and a blue plastic pair which matches Raiden's) which he changes at various points of the story, whereas Raiden only has just one (an orange plastic pair). Additionally, Solid Snake gets a longer bandanna, while Raiden gets three different wigs, depending on how many dog tags the player has collected from enemy soldiers (both characters get the stealth suit).
In the Substance edition, the player can play as Snake and Raiden in different outfits during VR/Alternate Missions in addition to their default sneaking suits. Snake gets to wearing his original sneaking suit from the first MGS, as his Iroquois Pliskin disguise and a tuxedo (only without a bandanna this time), while Raiden gets to dress up as the Cyborg Ninja (foreshadowing his transformation in Metal Gear Solid 4). The differences are more than superficial though, with each character having a different item loadout that affects which missions are available for each character and their level of difficulty. None of the Snakes can use the Grenade Launcher, whereas the only weapon available to Cyborg Raiden is the blade. The nude version of Raiden (the same one the player uses during the Arsenal Gear portion of the story) cannot use any weapon for obvious reasons, so all of his missions are appropriately enough labelled "streaking missions."
Following the introduction of changeable camouflage/outfits in Metal Gear Solid 3, subsequent games in the series have offered a variety of outfits for the player to change into. Most notably, Old Snake can dress as Altair from Assassin's Creed in Metal Gear Solid 4.
After completing certain achievements and gaining enough reward points in Uncharted: Drake's Fortune the player is able to change Nate's outfits at will, which include a baseball jersey, a t-shirt emblazoned with the Naughty Dog logo, and the wetsuit that we see Drake wearing at the very beginning of the game. The wetsuit is arguably Fanservice.
All over the place in Pokémon Battle Revolution; wins under various circumstances will give you new clothing articles, trainer titles, and other cosmetic rewards. And after clearing every Colosseum in the game, the trope becomes literal when you can win the species-themed outfits of some Colosseum leaders by defeating them again.
In the flash game, Battlegrounds 2, beating the game results in several new outfits (and the option to go bald) over the original boring three.
A stable in the Resident Evil series, where the player is awarded alternate outfits for his or her character as the standard prize for completing the game. The original game in particular allowed Chris and Jill to change from their default S.T.A.R.S. uniform into casual clothes.
The ports of the original game for the Sega Saturn, PC and Nintendo DS featured different alternate outfits that were not in the original PlayStation release. In turn, the Director's Cut version of the game featured new default outfits for Chris and Jill (as well as Rebecca), with the option to change back to their original defaults.
Resident Evil 2 has two extra costumes for Leon (which changes the way he wields the standard handgun), but uncharacteristically only one for Claire for some reason. Claire does get a new weapon in the form of the Colt S.A.A. and while it has a faster firing rate than her default handgun, it needs to be reloaded after every six shots. Said outfits were changed for the N64 port though, but the amount available remained the same and Claire still gets the revolver.
Resident Evil 3 Nemesis featured a boutique that allowed Jill to choose from five alternate outfits, including her old S.T.A.R.S. uniform from the first game and a cosplay outfit of Regina from Dino Crisis. The PC and Dreamcast port allows the player to choose Jill's outfit from the start and even offers two new choices.
Resident Evil Code Veronica was light on the alternate costumes, with only one being available for Claire and even then it was only usable on the Battle Game mode. At the very least it comes with its own loadout.
The GameCube remake of the first game has Jill's default outfit from Nemesis, as well as Chris' new S.T.A.R.S. uniform from Code: Veronica. The same game also has what seem to be movie cosplay outfits. Chris gets an attire VERY similar to what Brad Pitt wore in The Mexican and Jill gets Linda Hamilton's Sarah Connor outfit from Terminator 2: Judgment Day. Wearing Chris' outfit also changed Rebecca's to a cowgirl ensemble.
Resident Evil 0 gives Rebecca both the cowgirl costume from the first game's remake as well as a new leather outfit, and Billy gets a disco/gangster ensemble.
The PS2 and Wii version of Resident Evil 4 went so far as to have the second unlocked outfit actually make losing Ashley impossible. She wore a suit of full plate armor - all fire and weapons would bounce off her, and enemies would pick her up, and promptly fall over, dropping her. The player also gets an incredibly badass 30's mobster outfit for Leon. Well worth the time required to get it. The other costume set puts Leon back in his RPD police outfit (which in some versions gives the player the bonus defense boost offered by the Tactical Vest) as well as putting Ashley in a popstar outfit with a cleavage-revealing top, and having Ada wear her spy outfit from the "Assignment: Ada" minigame.
Resident Evil 5 gives the player two additional outfits to use on the multiplayer modes for the Chris and Sheva - but they aren't actually cosmetic awards, as they all have different weapons and starting items. Albert Wesker and Jill Valentine are unlockable as characters for multiplayer, who each have two different outfits and item loadouts.
Resident Evil The Mercenaries 3 D continues the tradition, with one costume for each character. Some of them (mainly Barry's and Krauser's) are altered versions of Chris' RE 5 alt costumes and Claire's suit is an offshoot of Sheva's RE 5 suit costume.
Resident Evil 6 has different outfits for each of the seven main characters for the Mercenaries mode: Leon gets a campy pirate outfit, Helena gets a "sexy policewoman" costume, Piers gets a race car uniform, Sherry wears her old (and far too small) clothes from Resident Evil 2, Jake wears a gangster outfit, Ada gets a quipao, and Chris, of all things, gets a decked-out samurai kimono.
Completing the 72-hour Mode of Dead Rising unlocks "Infinity Mode", in which your health is always slowly dwindling, requiring you to hunt down other survivors and kill them for their food. A Dead Rising day is two real-time hours, and there are achievements for surviving 3, 5, and 7 days - so for the 7 day achievement, you have to play the game 14 HOURS STRAIGHT. The 5 day reward is an awesome and powerful laser sword, but the 7 day reward? Arthur from Ghosts N Goblins fame's boxers.
And in Dead Rising 2, you actually start the game with those boxers.
Dead Rising really likes giving you clothes. All the DLC released so far has been new outfits, and most of the achievements will unlock clothes related to them, like a Rambo outfit, a Special Forces outfit, a Convict Jumpsuit, a Pro Wrestler's outfit...
In the mobile phone version of Dead Rising, you can find various blue items - boots, helmet, pants, jacket, and gun - which unlocks the Blue Bomber outfit.
Beating Clock Tower 3 will give you a key to a locked wardrobe from the first area of the game. Unlock it to find... you guessed it... clothes. To make things more interesting, the US and Japanese versions of the game have different outfits from each other.
Haunting Ground will usually give you clothes when you unlock a specific ending. You're given at least one costume near the end of the game (the patient gown) and Hewie can receive a "plushie dog" costume from beating Hard mode. Most of the outfits have special abilities: the plushie dog makes Hewie completely invincible, the brown/black fur costume makes him more aggressive and prone to attack Fiona but increases his attack/knockdown power by a great deal. Fiona's mascot (frog) costume allows her to use her backstep command without losing stamina. The "Illegal in some states" outfit gives her a whip, which has a wider range than her normal kick (the whip replaces the kick). Arguably, her best costume is the Texas Cowgirl, which when worn, causes her to panic much less often, possibly even more than the accessories you can equip her with. Add in a revolver that deals massive damage to enemies (even if it takes a few seconds to prepare) and unlimited ammo and the game suddenly becomes a lot less scary.
Starting from Silent Hill 3, you could earn alternate costumes for yourself (or, in game 4's case, your romantic interest) that don't do anything except in a few cases:
For playing through all 10 Extreme difficulty levels, your reward is the password for the God of Thunder outfit. Similarly, earning a 10-star ranking nets you the Golden Rooster password.
Travis can earn the Sprinter (allows him to run without tiring), Fireman (giving him an unbreakable ax), Ambassador (giving him a bitchin' ray gun), and Stalker (gives him night vision goggles) outfits.
The Fatal Frame series typically has certain costumes unlocked when beating a game on certain difficulties. The third game requires MULTIPLE plays on certain difficulties to unlock them all.
Finishing Drakengard 2 rewards the player with equippable Orbs which will change the main characters' appearances on subsequent playthroughs. Urick can be played without his mask, Nowe in peasant garb, etc.
Upon completing Dead Space you are informed that a new Military Suit has been unlocked for your next playthrough. It is something of a subversion, as the Military Suit actually increases your damage resistance. Dead Space 2 gave free armor for people who played through either the Ignition Tie-In game or the Severed DLC, both of which also had different statistics (also, playing through a game a second time would allow the player to collect Elite Versions of all the armor, which boosted statistics).
In Dead Space 3, however, this trope is played straight; you unlock the Engineering Suit for Isaac and the Security Armor for Carver, but unlike in previous games, different suits do not have different statistics or effects, which means that they are all purely aesthetic rewards.
Numerous sidequests in Deadly Premonition give the player character new suits to wear. Two suits, the Passion Red and the Saturday Night suit, do have gameplay effects: The first gives you more HP, and the second gives you more pulse. The rest just look fashionable and spice up your wardrobe.
Third Person Shooter
Red Dead Redemption has a large number of costumes which are unlocked piece by piece by doing various tasks, finding scraps of clothing hidden throughout the world map, etc. However, each has a gameplay benefit; gang outfits make it so members of the gang in question won't attack you, the Fancy Suit lets you cheat at Poker, and the 100% Completion reward is a Government Agent Suit, which lets you do whatever the hell you want without affecting your Honor. Though the only downside is with the game 100% completed, there is not much to do with it.
In Metal Gear: Online the points you earn at the end of matches, not during, can only be used to buy clothes that don't alter your abilities at all. Justified because the game is supposed to be fair, having the only out of combat bonus being what skills you equip, but also clothes affect the game in a different way. Instead of a direct "50% disguised" bonus, like in Metal Gear Solid 3: Snake Eater, you just reduce the amount you stick out to other players. If you have a giant red afro wig you will stand out more than if you went with a headband or helmet.
Turn Based Strategy
Advance Wars Dual Strike gives us a noticeably pointless example among some actually decent rewards (Like a New Game Plus). Although the alternate costumes are sometimes cool (Like Adder's Alice Cooper outfit) or downright hilarious (Jugger's suit and tie), the only time you even see the costumes are on the character's information screen— a screen which nobody who's played long enough to unlock the costumes will even bother to visit anymore.
Gadget Trial had 2 extra outfits for each of the girls, and they give certain strengths and weaknesses. Getting them, however, varies between ridiculously easy to quite difficult.
The second Penny Arcade Adventures game offered outfits to wear after completing certain tasks within the game or unlocking achievements.
Mass Effect 2. Gaining loyalty of crew members brings a new power... and an alternate outfit. In a nice twist, the unlocked outfits are all in the same black, silver and gold color scheme. The result is that gaining your crew's loyalty also has the effect of visually transforming them from a Ragtag Bunch of Misfits to a unified team of commandos. One of the more drastic examples is Jack. She usually wears pants, leather straps and nothing else. After the loyalty quest, she also uses a leather jacket. Standard Geth are grey and elite Geth are white, so Legion's plating color shift is a visual cue for him getting more badass. Gaining the loyalty of a squad member also increases the chances that that person will stay alive during the suicide mission, so there's that, too.
Dragon Age II: some of the companions' outfits change after you have romanced them or completed a certain personal quest. The changes range from small, such as the addition of a red handkerchief and the Amell crest after romancing Fenris, or something more drastic, such as a completely different outfit for romancing Merrill or a color change from white to black for Anders after completing one of his late personal quests.
The X-box/PC game Fable relied on a morality system partially based on how much you scared or impressed the villagers. You won the thief's clothing by completing a certain mission. People would run screaming if you were dressed in scary clothing, or throw themselves at your feet if you had "nice" clothing on. However, the "bad" clothes didn't work on the monsters.
Speaking to the right nobleman in the first Baldur's Gate results in the protagonist being given golden pantaloons by mistake. A further pair of silver pantaloons are available in the sequel as the ransom to be paid for the release of a kidnap victim found on a side-quest. Finally in the last game of the series a small band of newbie adventurers will, if you assist them, reward you with a set of bronze pants. All this would be totally useless if they weren't then able to be fashioned into Baldur's Gate's version of a Humongous Mecha.
The current version of the Xbox 360 dashboard gives Avatar awards which you get by... getting achievements. Seems redundant.
Daggerfall. As you progress through a Knightly Order's ranks, if you should join one, they award you with a piece of normal armor, completing a full set when you're done. Fortunately, there are other minor perks at different levels of promotion, and they also give you a house when you get to the highest level.
As you progress through the Imperial Legion's ranks, if you should join them, they award you with a piece of armor, completing a full set when you're done.
For completing The Seven Trials of the Nerevarine, you get a symbolic ring. For each of the four Ashlander tribes that recognize you as the Nerevarine, they give you a piece of symbolic clothing. For each of the three Great Houses that recognize you as the Hortator, you get a piece of jewelery. Ultimately, these successes yield a gauntlet. Only some of the enchantments on this garb are considered useful.
After Caius Cosades is finished giving you quests for the Blades, before departing back to Cyrodiil, he gives you his enchanted clothing. Yes, apparently he did own a shirt, but doesn't wear it.
In an inversion, there is a piece of armor in the game that you shouldn't wear belonging to the policing force of the city Vivec.
To officially free Argonian and Khajiit slaves, you need to find the key for their enchanted shackles. You get to keep those shackles.
The game gives you a clothes reward for rescuing someone who might just be the avatar of a local deity. Like many other free garb it has relatively weak enchantments on it, so this is not as phony as it sounds. (?)
There's one quest that involves setting a group of ghosts to rest. Each ghost rewards you with a unique piece of equipment. In a sort of Deconstruction, one of these unique items is... a pair of soiled trousers.
Many Imperial Cult quests give you enchanted clothes. Some of them are actually useful.
For completing the central plotline, the Council awards a custom suit of Imperial Dragonarmor.
Oblivion also follows Morrowind's precedent for rewarding quest completions with trinkets and clothing of minor value and varying utility.
Interestingly, in Fallout 3, most clothing gives you bonuses to stats and/or skills (e.g., most hats give + 1 to Perception for keeping the sun out of your eyes, and wearing sexy nightwear gives + 1 Charisma), making rare outfits one of the better rewards in the game!
Vampire: The Masquerade - Bloodlines features a series of 'mostly for fun' quests which reward you with girlie posters featuring some of the female characters from the game. The posters don't do anything ... they just sit there on the walls of your haven. And on the walls of your old haven if you've moved during the game. Hmmm...
In the German RPG Drakensang (published August 2008, English version expected beginning of 2009) there is a place where you can find a false beard, a Hawaiian shirt and a paper bag (to put over a character's head). The beard can be used to give a dwarf character a beard again, who had shaven it off as a sign of his disgrace after allowing his former boss to be killed while he was a bodyguard for him
Star Wars: The Force Unleashed has the Sith Stalker armor (Dark Side ending), Ceremonial Jedi Robes (Light Side ending) and over a dozen others sold as DLC.
Played straight (and for comedic effect) in the second Knights of the Old Republic. Exile wakes up in his/her underwear and has to brawl through Peragus Station. Both Kreia and Atton will snark about your state of undress. One of your "rewards" is a miners' uniform in your size.
Played straight in Assassins Creed II; finishing various parts of the game gives you capes that make it more likely that you'll be ignored by the guards. In That One Sidequest, you can get an additional cape by collecting 100 feathers all around the world, in hiding spots and nigh-impossible to see niches (which turns guards against you.)
Also, after you navigate the huge mausoleum — tombs of six of the world's most famous assassins and revealing secrets hidden from mankind for over 500 years, you get some clothes.
Which have the best damn armor stats in the game, and never need to be repaired, so it's all good.
This is re-done in the next two games. Revelations even had two sets of them!
Revelations also unlocks a Desmond skin for Ezio once you complete the five Desmond sequences. This counts because Desmond in this game has exactly the same face as Ezio (which looks odd on his younger body). Amusingly, Desmond also takes the place of Ezio in cutscenes if you use his outfit.
Grand Theft Auto Vice City has this as well; upon getting 100% completion, you gain a t-shirt which proclaims I got 100% completion on Vice City and all I got was this shirt (see the page pic). Admittedly, you also get infinite ammo and 3 bodyguards, but still...
In Grand Theft Auto IV, if you kill Playboy X, you get his rooftop studio pad. If you change clothes there, you'll discover that at that location and at that location only, you can switch to the outfit of Claude from Grand Theft Auto III.
Non-Video Game Examples
Anime and Manga
.hack did this in the manga. You solve a puzzle, beat a monster... and are rewarded with schoolgirl and maid outfits.
The god-awfulEroge the protagonist and his friend make in Welcome to the NHK includes a end-choice where you can choose which outfit the lead girl wears next time around, including a skimpy sea-shell bikini.
Gunslinger Girl. Someone notes the expensive perfume and coat that Jose has bought his cyborg Henrietta. He points out that such gifts actually constitute her salary, because these brainwashed killers work for nothing.
The Bone prequel Tall Tales contains a story in which Fone Bone and Phoney Bone follow a treasure map to a chest containing...Phoney Bone's dirty clothes, buried as a reminder for the two of them to do the laundry.
In the world of Harry Potter house elves are freed if their owners give them a reward of clothes (so you could say the reward is freedom, via clothes). Cue Harry tricking Lucius Malfoy to give Dobby a sock and Hermione leaving piles of clothes all over Hogwarts.
Unfortunately, most elves other than Dobby are Happy in Slavery, so Hermione's gesture just insulted them.
This seems to be Adam's primary trophy on Man v. Food, despite whatever inhuman amount of food he consumes during a challenge.
In Have Gun — Will Travel, Paladin once did a job for a high-class tailor, and for payment would only accept two custom suits a year for the rest of his life. He noted it was actually more expensive than his standard charge; he intended to live for a very long time.
Parodied in Sluggy Freelance where the MMORPG "Years of Yarncraft" has underwear as the reward for completing the first quest. This actually becomes an important (in-game) plot point during a later, high-level raid. To be fair, as Torg notes, he could really use underwear.
In The Order of the Stick after goblin archers killed the (illusion) heroes, the goblins changed to t-shirt that says: "I killed a PC and all I got was this lousy t-shirt!"
One Mac Hall strip denotes the delight of the author's Final Fantasy XI character finding actual pants that actually cover her legs; it's a reference to a previous strip that showed how stripperiffic all other "pants" were.
In Homestuck, your reward for successfully rising to the God Tiers is a variation on immortality, mastery over the aspect you were chosen for... and rather nifty 'pajamas' varying on your class and aspect. A 'god-hoodie' if you will.