In Naruto Shippuuden, a mirror match occurs simultaneously Gai's team, each having a copy of themselves. They eventually beat their copies by realizing that they can become better than their copies, because the copies don't improve but they do, because they've sworn to improve every day.
During his training with Killer Bee to control the Kyuubi, Naruto is faced with a mirror copy of himself...or something. He beats it by hugging it.
A one-shot character in Hikaru no Go attempts to stalemate Akira Toya by mimicking every move Akira makes, starting by taking away the spot in the center board. Akira wins anyway by tricking him into a position where he manages to capture, breaking the guy's strategy. (Which is later revealed to be low-grade and easily countered).
The villain in Saitama Chainsaw Shoujo shows some doppelganger abilities when she takes the physical shape of protagonist Fumio, complete with clothing, equipment, and muscle-memory of her fighting style.
The whole plot of Pokémon: The First Movie revolved around Mewtwo luring trainers to his island and making clones of their Pokémon, leading to a climax which sees each Pokémon fighting its clone.
One chapter of Magic Kaito had Kaito Kid facing an android double that could replicate his every move. Kid defeated the double by shooting himself in the head. Kid's gun was a toy that fired playing cards, resulting in a sore ear. The robot's gun was a weapon that fired bullets, resulting in a trashed robot.
Subverted in Oto x Maho, where Kanata faces off with an evil duplicate. Kanata prefers physical attacks, while the Evil Twin can only use magical attacks.
In the Sonic the Hedgehog anime, Metal Sonic is programmed to be an exact copy on regular Sonic, and it is even implied that they share a mental link (see the part when Sara is kicking Metal Sonic in the head, and regular Sonic is writhing in pain). The two are constantly seen running into each other, until finally, Sonic says this quote:
Sonic: "You might know everything I'm going to do but that's not going to help you since I know everything you're going to do! Strange, isn't it!?"
Erza Scarlet vs. Erza Knightwalker in Fairy Tail. Natsu was freaked out the moment he saw those two fighting, as Erza is the only person he was ever afraid of.
In Digimon Adventure, Etemon trapped the Chosen in an arena and set a captured Greymon on them; he also arranged a trap so as to trap all of the Chosen's partner Digimon except Taichi's Agumon, whose evolved form is Greymon. Needless to say, the two fight.
In Yu-Gi-Oh!, during the Orichalcos arc, Yami and Yugi end up facing each other. Yugi uses a copy of Yami's deck, except it has the Seal of Orichalcos in it.
In Yu-Gi-Oh! GX, Judai and Edo's second duel seemed to be a mirror match at first, but it turns out that Edo had splashed some Elemental Heroes into his deck to fool everyone, and his real deck is Destiny Heroes.
In Yu-Gi-Oh! 5Ds, one mini-arc featured Jack Atlas dueling against a robotic copy of himself who uses the exact same cards. The only difference is the copy uses three Red Demon Dragons instead of one. Jack gets curb-stomped the first time, but wins the rematch.
In the manga, Crow duels a dark copy of himself who uses the same deck and strategies as him. However the copy has monsters that Crow doesn't have in his deck.
In the first arc of Saint Seiya, the four main characters have to fight against the Black Four, which conveniently use dark-armored variants of their own respective clothes/armors. They even have slightly different variations on the heroes' signature techniques.
The final episode of Black★Rock Shooter has a battle between Mato in Black Rock Shooter's form versus Insane Black Rock Shooter. Mato started out with a severe disadvantage because her Healing Factor was slower, she lacked Insane Black Rock Shooter's immunity to pain, and she couldn't bear to hurt anyone. However, when Mato is finally motivated to fight back, she proves to be just as powerful as her counterpart and eventually defeats her with a Combined Energy Attack.
Chess and Draughts/Checkers are obviously Mirror Matches, although it could be claimed that the fixed move order makes White and Black rather different prospects to play despite being otherwise identical.
The original, very brief appearance of Spider-Man's clone was basically a one-issue, pretty cool Mirror Match fight that ended with the clone killed in an explosion. Twenty years later, the clone got brought back for a convoluted storyline that dominated the title for a couple of years.
An even earlier example of this came in Captain America #156, where Steve fought an insane 1950s impostor, complete with both wearing the Captain America outfit during their showdown. In addition, said impostor even looked like Stevenote He had been so devoted to Cap's original exploits, he volunteered to literally become Steve Rogers when the FBI wanted a Captain America to help them against the Communist menace in the 1950s., adding yet another layer to this all-American mirror match.
Power Girl was once sent to the recreated version of Earth-2, only to find another Power Girl already there. The alternate Power Girl did not respond well to this "imposter". Later, Power Girl went up against "Divine", a black-haired evil clone of herself created by Maxwell Lord.
In Rat Queens, issue 3, Violet has a mirror match with her twin brother, Barrie (Barrie implies that they would look even more similar if Violet had not shaved her dwarven beard. She comes out on top of the fight and sends Barrie packing back to dwarven lands.
In Superman III, Superman is exposed to some flawed synthetic kryptonite and turns "evil" (read: superpowered Jerkass). His inner conflict is played out onscreen when Clark Kent manifests in front of him and they fight until Clark wins, then tears open his shirt revealing the untarnished S-shield and flying off to undo the damage he did when he was "evil", ending the only enjoyable scene in an almost universally reviled movie.
Subverted in Scott Pilgrim vs. The World, when Scott meets Nega-Scott. There was only the vaguest of foreshadowing and no real explanation, although several interpretations are possible. It looks like they're going to fight... but then they get to talking, and it turns out they have a lot in common. They decide to meet for brunch the next week.
It plays out much differently in the comics, as we learn that Nega-Scott has a much larger purpose. He's a manifestation of Scott's screw-ups when it comes to relationships and himself in general. Instead of defeating Nega-Scott, our hero has to come to terms with his dickery and has to merge with Nega-Scott in order to become a better person.
The awful straight-to-video film The Replicant has Jean-Claude Van Damme play a serial killer and a clone created by the government to track him down. The clone has some sort of connection with the killer but a much nicer personality. In the end, they face off in a fight. The viewers expect to see a cool fight between two Van Dammes. Instead, they got an attempt at one, as the doubles try to punch and kick one another, only to perform the same exact move (but mirrored, for some reason) and strike the other's first/leg instead.
The One ends with a fight between two super-powered Jet Lis. While the villain Yulaw has more practice with his enhanced speed and strength, the hero Gabe is on a Roaring Rampage of Revenge and has been practicing martial arts daily. In the end, their style (Yulaw uses the more aggressive, straight-line Xingyiquan style, while Gabe sticks with the subtle, circular Baguazhang style) and terrain (the start of the fight is on a tight catwalk, and the end is on an open factory floor) decide the outcome. And yes, this is the best part of the movie, especially when both of them go to Super Speed, and we see the fight from their perspective (i.e. Time Stands Still).
A rare live-action version in Oblivion (2013).Jack Harper-49 vs Jack Harper-52.
In Book 19 of Lone Wolf, the main antagonist is an Evil Knockoff called Wolf's Bane. The main plot involves Lone Wolf chasing his evil impostor to try to bring him to justice. When you finally face him in combat, he has the same stats and abilities as you, the only difference being your respective Endurance Points if he was wounded earlier.
A few of the Fighting Fantasy gamebooks that allow the player to use magic typically include a "Creature Copy" spell. When cast, the spell creates a magical duplicate of whatever monster you're facing to fight it.
In the third volume of GrailQuest, one of the enemies is a distorted version of yourself created by looking in a magic mirror (the only difference is that it has only half your current LIFE POINTS).
Rand from The Wheel of Time series fights a more or less literal Mirror Match when a "bubble of evil" spontaneously causes his reflections to jump out of mirrors and fight him to the death. Eventually he starts wising up to the situation and extinguishes his Flaming Sword, causing his reflections to do the same (to their confusion) and making the fight slightly easier.
An example from the Star WarsExpanded Universe; during the Force Heretic novels, Jedi Tahiri Veila has a series of nightmares/hallucinations/Force-trance-somethings which pit her again various aspects of herself, including her Vuuzhan Vong implanted personality (looong story), which takes the form of - you guessed it - a mirror image of herself. Interestingly, they're actually mirror images: Tahiri is left-handed and Riina right-handed, and that's the only way to distinguish between them.
Hell, even Luke Skywalker has to deal with an evil clone of himself in one novel; the clone was imaginatively named "Luuke" Skywalker. In defense (as someone elsewhere noted), it was named by a Cloudcuckoolander villain...
Every Jason X novel except Planet of the Beast had Jason battle a clone.
This is used quite a lot in Power Rangers, being a nearly once-seasonally tradition. Often they were led by a Monster of the Week. Zeo and RPM (so far) are pretty much the only seasons who haven't had it in some form - if not identical copies, then an Evil Counterpart team will be featured, like Space's Psycho Rangers, the Spirit Rangers and Five Fingers of Poison in Jungle Fury. Oddly, only once (the very first use of the gimmick waaay back in the original series) were they used to ruin the Rangers' good name, and never have they been used to pose as a friend and backstab a good Ranger.
Oddly, the Sixth Ranger seldom gets a copy. But sometimes Tommy's subverted it, facing his past selves.
Disappointingly averted in The Secret World of Alex Mack. Alex gets an evil duplicate, but despite both of them having telekinesis and electric powers, they never actually try to fight — Alex winds up just chasing her evil twin around until they recombine.
Played straight in Charmed when Paige and Phoebe and their evil Mirror Universe counterparts fight. Leo comments that they are too equally matched and neither side could win, so the fight went on and on until they realized this, called a truce, and formed an alliance instead.
Tuvok Impostor: Logic states that we are evenly matched. Tuvok: Your logic is flawed. (shines a flashlight into his eyes and beats him up)
Lord John Roxton gets an Evil Twin in one episode of Sir Arthur Conan Doyle's The Lost World after he is cursed for disturbing a graveyard's peace. The protector takes the ruthless and violent part — basically the hunter part — out of him and gives him a life of his own. Evil!Roxton tries to kill the good one, using Marguerite as bait. It ends in a Mirror Match.
Averted in the sequel/remake, as this version of KARR is a Transforming Mecha (and yes, the fact that he's still voiced by Peter Cullen, known for voicing Optimus Prime, is a bonus), while KITT can only transform into other cars.
In Supernatural towards the end of Season 6, Sam has a confrontation with Soulless Sam after Castiel brings down Death's Wall.
A Highlander episode has Duncan go evil after killing a former friend of his and absorbing his dark essence during the Quickening. Eventually, Duncan goes into a cave and has a Battle in the Center of the Mind manifested as a swordfight between him and an evil double. Somehow, this also ends in a Quickening, although there's no body of the evil Duncan.
The WWF tried to pull off a Mirror Match in live action at Summerslam 1994, with a match pitting The Undertaker against...The Undertaker. Unfortunately, this proved impossible to pull off with any degree of realism, as the false Undertaker they got was quite a bit shorter and slimmer than the actual Undertaker. However, this didn't stop Vince Mcmahon from proclaiming, "It's like looking into a mirror!"
They did this again at Vengeance in 2006, except this time it was Kanevs Kane.
WWE have tried it once again. This time, it's Sin Cara vs. Sin Cara, and surprisingly, it doesn't suck.
Sabu once faced off against a masked wrestler known as the Doppleganger, who was able to imitate Sabu's moves very well. Under the mask was Shaggy 2 Dope of the Insane Clown Posse.
In Changeling: The Lost, one of the central conflicts for changelings is how they deal with their fetch, the magical imposter that was left behind when they were abducted. Responses to coming back after the horrific ordeal that is service to the True Fey is hard enough without having to deal with something that wears your face and has been living (or ruining) your life while you were away. Depending on how the Storyteller wants to play things, the fetch could be a malicious sociopath out to ruin the changeling's good name, a dark reflection of the changeling (or even a light reflection—nothing stops the fetch from being a better person than the changeling it replaced), or an innocent bystander with no clue why this horrible creature it dreams about wants to kill it and take over it's life.
Dungeons & Dragons has a magic item called the Mirror of Opposition, which creates a clone of anyone looking into it with all the character's items and abilities, but the exact opposite alignment (Lawful Good produces a Chaotic Evil clone, Chaotic Good produces a Lawful Evil clone, while True Neutral produces a clone of random allignment, and so on), resulting in a big fight after which the clone and its items vanish.
It's also used in the Tales of the Sword Coast expansion of Baldur's Gate. In the sequel, Big Bad Jon Irenicus pulls a similar trick during the battle in Spellhold. On a similar note, high-level mages can use the Simulacrum spell to summon a (weaker) copy of themselves.
The D&D module "Quest for the Heartstone" has the climactic battle a one on one fight between each Player Character and a duplicate created by the Heartstone. Victory meant you stay yourself, defeat meant you change to the opposite alignment. The Players have a slight advantage over their duplicate in that the duplicate had 10 hit points less than them.
Various The Legend of Zelda games have the Dark LinkMini-Boss, who got various levels of character development, but was essentially a shadowy version of yourself. The Legend of Zelda: Ocarina of Time subverted the intuitive Mirror Match expectations by equipping Dark Link with absolutely none of Link's tools and weapons, except for shady counterparts to the Hylian shield and the Master Sword. As if to make up for this, it gave Dark Link a few added abilities, such as the ability to vanish and reappear behind Link when struck, and the ability to paralyze Link by hopping up to balance atop the blade of his Master Sword. This ability is only applicable when Link thrusts straight on, so it can easily be avoided. But it's worth getting caught in at least once because it's just that Badass.
The Bonus Boss in the GBA remake of The Legend of Zelda: A Link to the Past is actually four Links that represent the colored Links you played as in the multiplayer game. Not only do they possess the Golden Sword and the Mirror Shield, along with basic sword slashes, but each color you fight can do everything the last one did and gains a new move. note In order: Green can use the Pegasus Boots, Red can use the Hurricane Spin, Blue has the Magic Cape and Roc's Cape, and Purple can shoot fireballs from the tip of his swords (doesn't quite mimic Link's energy attack from his sword when his life meter is at full, but the concept is the same) and takes twice as much damage.
Dark Link in Zelda II: The Adventure of Link serves as the game's Final Boss. Link has to fight his own dark self to prove his worth for the Triforce of Courage and the boss is no slouch. Dark Link can almost block every attack you throw at him with perfect timing and strike you when you least expect it.
In Castlevania Judgment, both the combatants have special comments and a (shared) unique win quote for a mirror match. Notably, Aeon, the Guardian of Time, believes his clone to be a threat to all of time.
Darksiders does this when you get to Eden, where you're forced to fight a particularly bastard-ish version of yourself that can use some of your limited use moves as many times as he cares.
One of the recurring bosses in Castlevania is the Doppelganger, which imitates the player's appearance, moves, and (sometimes) stats.
Some levels of Blaster Master have mooks that look like gray versions of the player character.
God Hand provides two examples: The first is Azel, the owner of the other God Hand who prefers to call himself Devil Hand as a contrast to the player character, Gene. Both characters use essentially the same moves on one another, and can even engage in Fist of the North Star-esque pummel duels. The second example is the final arena match, where Gene faces a carbon copy of himself (actually a reskin of Azel) with both God Hands for 99,999 gold.
The original Devil May Cry uses this trope quite literally when Nelo Angelo aka Vergil emerges from a mirror to battle you. Both brothers have similar abilities (swords and projectiles).
The third one featured a Doppelganger boss. Defeating it would earn you the Doppelganger style, where you create a shadow of yourself that copies all of your moves.
Averted in Ninja Gaiden III for the NES. The fifth boss is Ryu's doppelganger, but he has his own sprite (which is twice the size of the player's) and attack patterns. The doppelganger is revived as the boss of the next stage, who has a completely different form.
Bayonetta uses this trope quite literally as well. And how? She fights herself at the end the "Angel Slayer" bonus Chapter.
During the final stage's Boss Rush in Cannon Dancer, Kirin confronts a gray-colored clone of himself called Fake, who comes out of a mirror. He can do every one of Kirin's moves, but can't use any power-up/energy double.
In Quest for Glory III: Wages of War, the party the Hero has assembled fight mirror duplicates of themselves (created by magic mirrors, of course). The evil duplicates blatantly cheat by being significantly more powerful than the originals. The Hero's own fight is unwinnable without assistance.
In Star Trek: 25th Anniversary for PC, the final battle is against a duplicate of the Enterprise, but tricked out with plasma torpedoes in addition to the normal weapons and escorted by two pirate vessels. It's easily the hardest part of the entire game.
Technically, the escorts show up after about a minute, so you still have this much time to defeat the other Enterprise. Good luck with that.
The final boss in the NES version of Double Dragon is Billy Lee's (the player character) twin brother Jimmy, who has all the same moves as the player and more health. This is actually a carry-over from the arcade version, in which the game forced both players to fight each other at the end if they defeat Machine Gun Willy together (Jimmy Lee was originally the Player 2 character in the arcade version).
The NES version also has a one-on-one Versus Mode where you could compete against the computer or another player as one of six characters (Billy Lee and five enemies from the main game). For some strange reason, the developers decided to use larger sprites for all the characters in Versus Mode (except for Abobo, who uses the same sprites from the main game and looks oddly proportioned compared to the other Versus Mode characters) and as a result, only same character matches are allowed. When Billy is chosen, the Player 2 variant will be colored like Jimmy (red clothes and blond hair).
In Double Dragon II (both, arcade and NES versions), the player must fight against a clone of their character in the enemy's hideout. If there's a second player present, then there will be two clones instead of one (one for each Lee brother). The clones have almost all of the same moves as the player, along with the ability to throw projectiles and possess the player from the inside to drain their health. The clones are the final bosses in the arcade version and the penultimate bosses in the NES one.
Jeff, an enemy character who appeared in the first two arcade games (and the Sega Master System version of the first), narrowly averts this by being a head-swap of the Lee Brothers and not a full clone. However, when Jeff returned in Super Double Dragon for the SNES, he was made into a complete palette swap of Billy Lee with tanned skin and a green outfit. Oddly enough, Jimmy, who was a palette swap of Billy up to this point, was made into a head swap in the SNES game.
In Streets of Rage 3, the third boss is a robotic duplicate of Axel Stone named Break. He looks exactly like Axel, only with blue gloves to distinguish him.
In the original game, Onihime and Yasha (aka Mona and Lisa), the twin bosses at the end of Round 5, were palette swaps of Blaze. However, when they returned in the third game, they were given new sprites.
In Undercover Cops, the player must fight against clones of all three heroes before fighting the final boss.
In Captain Commando, the boss in Stage 8 is Doppel, who can transform himself into an identical copy of the Commando he's up against. If more than one player are facing him, then Doppel will split himself into the required number of clones to fight.
The trope name comes from the Mortal Kombat series of video games. In the original Mortal Kombat, you fought a clone of the character you selected before going on to the two-on-one Endurance Matches. The early-90s Mortal Kombat comic referenced this, with the queen of a warrior tribe who just happened to look and dress like Sonya, called Queen Aynos.
And, of course, Shang Tsung could turn the fight into a Mirror Match by transforming.
However, the earliest incarnation of this trope predates Mortal Kombat by at least seven years. Ultima IV had the player's party fight evil opposites near the end of the game; there may be earlier examples.
The Konquest mode of Mortal Kombat Deadly Alliance always ends with the selected character facing themselves in a 3-out-of-5 battle. Usually the battle is divorced from the backstory that previous Konquest missions had been giving.
Street Fighter II: Champion Edition was produced largely to allow this sort of match - the original Street Fighter II didn't allow for mirror matches (except for the SNES version shown above, which featured a code that could be inputted when the game started).
The Street Fighter II manga by Masaomi Kanzaki had a story arc where the four main Street Fighters (Ryu, Ken, Chun-Li, and Guile) had to team up with the Four Shadaloo Devas (Bison, Sagat, Vega, and Balrog) in order to defeat their evil clones.
Gouki/Akuma in Super Street Fighter II Turbo actually had an alternate ending if he defeated himself as the True Final Boss. Unfortunately the text that explained the ending was cut from the American version - basically he fought his own darknessand won.
Later games actually gave some characters special intro animations when this happens, usually interacting with their clone before getting into fight position.
Similarly, Melty Blood characters fighting themselves will generally comment on it after the match ("Geez, you're just a fake, but your hair is so pretty...!"). To say nothing of the many, many Doppelgänger characters in the series.
An interesting Mirror Match happens in Guilty Gear X2 in Axl Low's story mode. He fights a version of himself from the future. The interesting thing is that unlike most fighting game mirror matches, both combatants look exactly the same, including colour scheme (sometimes making it hard to tell who is who) yet future Axl is using Axl's EX moveset and is invulnerable to normal attacks. Turns out future Axl traveled back in time just to give his past self a pep talk...and a beating apparently.
And taken even further in Tatsunoko vs. Capcom with Yatterman-1. To avoid players from questioning why would they be summoning the same giant sentient robot dog, the default Yatterman palette summons Yatterwan (said giant sentient robot dog) whereas the alternate color scheme calls out Yatterpelican (a giant sentient robot pelican). This has been taken down in the US version though, as it poses unfairness as Yatterpelican has a higher angle for the flame attack.
Again in Tatsunoko vs. Capcom, Gold Lightan has a quirk when choosing his alternate palette. Aside from turning silver, his name changes to Silver Lightan, and all of his voiced attacks with "gold" are changed with "silver". Yes, that means he shouts "SILVER LIGHTAAAAAAAAAAAAN!"
In M.O.D.O.K. vs. M.O.D.O.K. matches, whoever wins will make a comment about needing to remember to lobotomise his clones in the future.
In the Kattelox Island stage, Tiesel usually cheers for Tron when she's fighting. When two Trons enter the fight, he looks at them in utter confusion.
In SNK vs. Capcom: SVC Chaos, every single possible character matchup has its own dialogue. Right down to said Mirror Matches. Kyo even references the rampant clones he had running around during the NESTS saga.
Since the very first game, Nakoruru's 2P color was hinted at being an alternate personality of her by giving her win-portrait (and sometimes, official art of it) a malicious smile. This was used in her Bust/Rasetsu versions since the third game, but while those would eventually spawn a different character named Rera, the "purple" Nakoruru would still survive as Nakoruru's alter ego, who would be made into a secret character for Samurai Shodown 6.
The third game in the series created alternate versions of each character, giving them different special moves to expand the gameplay, as well as a shape-shifting mid-boss who would transform into you for a mirror-match. However, mirror matches against the CPU were handled very poorly: Not only would the mid-boss transform into the exact same version of the character you were using; you were required to also beat your actual alter ego...who would be the same version as you and the mid-boss. Then, in the fourth game, each character has a fixed set of enemies he/she can fight, so it actually averts CPU mirror matches; unless you were using Amakusa, who returns as a boss and in fact uses the opposite style you picked for your character.
The same applies to One Must Fall: 2097, in Story mode for all playable characters (in Tournament mode, you create your own pilot, who has no doubles in the tournaments which come with the game). All characters notice what's happened (it isn't played as impersonation) and seem to consider meeting themselves normal. Example from Milano: "When I think about you.../ ...I kick myself..."
The best part? Angel vs. Angel is a plot point if you know her backstory.
The King of Fighters games play with this trope as well. In KOF 2003, Terry Bogard comments that "I just changed my image and I already got impersonators!" if he beats the Fatal Fury Team.
In KOF'97, since the New Face Team is both a regular entry and a boss team they're given dialogue between them and their alter-egos that state that they're clones of the CPU characters.
In KOF XI, having Kyo win a mirror match has him, much like Spidey before him, take the mickey out of this:
Kyo: Just how many clones of me are left? I could make a baseball team out of me!
Lampshaded when Solid Snake calls Colonel Campbell on his codec during one of these, and both Snake and Campbell are puzzled about where the other Snake came from. Snake being a clone, Campbell brings up the possibility of the other Snake also being a clone, but ultimately decide not to let it bug them too much.
Also used in the end part of the subspace emissary where Tabuu takes the pieces of the world the bombs detonated in and puts them together to make a maze, which includes boss characters already fought and a rainbow colored version of all the playable characters.
In the Neo Geo fighting game Kabuki Klash, the loser of a Mirror Match was shown to actually be a Kitsune (if you're playing a female character) or a Tanuki (if male) imitating the winner on the victory screen. (Where they usually slump over or kneel in defeat, a puff of smoke reveals a little kitsune/tanuki instead.)
In Waku Waku 7, the penultimate fight for every character is a shadowy clone of themselves.
All three Art of Fighting games, but in Art of Fighting 2's story mode, the characters would have some funny dialogue to exchange pre-match in story mode.
Interestingly most characters in Bleach: Shattered Blade do have special opening quotes for fighting themselves, although only a handful have special victory quotes where they dismiss the quality of their fake. The 2nd Player versions of the characters don't usually have any special quotes.
The makers of Magical Battle Arena seem to think that normal Miror Matches are too wimpy. After all, why else would they sic five duplicates of your character at you for the obligatory Mirror Match stage?
The fact is somewhat mitigated by the application of Conservation of Ninjutsu. The clones have about half your defense, and hitting them builds up your Charge Meter faster than hitting a non-clone.
SoulCalibur 3 has these built into (almost?) every character's story mode. They appear to be the externalized representation of some internal conflict for the chosen character, and the story always moves on regardless of whether or not you win, albeit usually in a different direction.
Dissidia: Final Fantasy, of course, as a fighting game. The characters can have some interesting lines for their duplicates; ranging from a Mythology Gag (Cecil repeating his line before facing himself in his own game: "This is a fight for me and me alone."), to the utterly hilarious.
Cloud Strife got a serious mood whiplash with his mirror match quotes. His first was a somber "If I win, will my sins be forgiven?" and in Duodecim that got changed to "Not you again!" in a more humorous tone. This actually makes sense when you consider that Duodecim is a prequel, and in the story line of the prequel he was actually fighting for the side of Chaos.
Dissidia 012 introduces a new type of battle piece in the Scenario 000 story mode, which pits every member of your party against an exact duplicate of themselves with the exact same moveset, abilities, equipment, and stats.
In addition, Sephiroth faces another Sephiroth as an in-game representation of him committing suicide.
Eternal Fighter Zero not only has standard mirror matches (complete with unique win quotes), but in Memorial, you can set up a match between Kanna and Misuzu. If you've played AIR, you know exactly what is wrong with this matchup.
If you beat Real Bout Fatal Fury as Geese Howard (who is the final boss), your ending shows Billy having Face Doodling the word "nisemono" (impostor) on the defeated Geese's face.
Arcueid: Look who it is. Are you the real one? Ciel: That is understandable. I had to kick around many of my fake selves before I came here. Arcueid: If you're involved in something that troublesome, you're the real one. So, how are you doing Ciel?
Breakers (and its sequel Breakers Revenge), a Neo-Geo fighting game by third-party developer Visco, had a unique approach for justifying the presence of mirror matches in the single-player mode. The computer-controlled clone of the player's character will have a different name tag and a unique palette used exclusively by the computer, implying that the clone character is actually a different fighter who uses the same fighting style.
In the NES version of Teenage Mutant Ninja Turtles Tournament Fighters, this feature is available for every fighter except Hothead (a humanoid dragon based on the Warrior Dragon from the comics). The game claims that "The Dragon Spirit [inhabiting Hothead] would never allow such a thing," but in reality, the game's memory won't allow such a thing. If you use a Game Mod to do it anyway, it will cause massive flickering in the sprites.
Persona 4 Arena has special theme songs that play for mirror matches; specifically, the battle themes from previous Persona games (Reach Out To The Truth for P4 characters, and Mass Destruction for P3 characters).
Primal Rage. No matter who you choose to play as, you'll always fight yourself along the way.
Dynasty Warriors 3. The battle of Fan Castle is a fight between allied forces (Wu and Wei) and Shu forces (led by Guan Yu). If you set up a custom battle on this map, choose the Wu forces, and select your character to be Guan Yu, he will comment in the opening cutscene, "I am my own opponent? This will be difficult." This was carried over, quote and all, to the recreation of the stage in 7: Xtreme Legends.
In Warriors Orochi 3, all of the player characters (when they are in your party) have a comment for facing themselves in battle, since the plot of the game involves time travel.
In Guild Wars, one of the main quest chains has you fighting a mirror copy of yourself, only all of its stats are maxed, and even if you don't equip any skills, it's got a big sword to hit you with. Or a bow if you run away. Oh, and it's max-level, while you can reach it several levels below your own max. Solution? Equip skills that require a health sacrifice, or hexes that the enemy triggers by either spellcasting or attacking. Either way, the AI is stupid enough to kill itself for you.
However,it must be noted that before the expansions came out, you could have only been able to change your secondary profession AFTER completing said mirror match, so unless you knew beforehand and picked necromancer as a secondary profession to gain access to health sacrifice skills? your Mirror match could have been much more difficult.How difficult your mirror match is is really dependent on what profession you chose. A warrior could have an easy time, whereas a healing monk player could tear his hair out in frustration.
Kingdom of Loathing claims to have this in the final quest, with the Mirror Class monster. You can't hit it either, and it blocks anything you do to it.
The first is a quest in howling Fjord, in order to "purge your evil." You have to meditate until it manifests as a copy of your character, unfortunately, this one has no skills other than attacking you, which leads to a rather disappointing fight.
The second is herald Vol'azj in the Old Kingdom, once during the fight (twice on heroic) he casts insanity on the party, causing shades of the party to spawn where they were standing and attack you, these do use abilities, but besides iconic class abilities, they generalize the images to what their class is good at (druids and priests will only heal, death knights will death grip, ect. ect.).
Usually played straight in League of Legends, but ranked games (and custom if you want) use draft pick, effectively barring mirror matches. The game does you the favor of putting colored circles around most of the persistent AOE effects in order to differentiate the source, while some of them are virtually impossible to distinguish.
In Kirby and The Amazing Mirror, the intro cutscene shows Meta Knight facing off against his mirror self (called Dark Meta Knight in the game). He is quickly defeated. Kirby's mirror self (known as Shadow Kirby in the game) appears occasionally as an enemy - defeating him will give Kirby a random powerup.
Super Mario Galaxy pits you in races against Cosmic Mario for a star. Not quite a fight, but a match in terms of platforming capabilities (however, Luigi's duplicate is much smarter than Mario's).
In certain missions in Super Mario Galaxy 2, Cosmic Clones of Mario will follow your route through a level and mimic your actions exactly until you accomplish some objective, at which point, they'll disintegrate and turn into star bits. You're usually okay if you keep moving and don't retrace your route, but if you make even the slightest slip, they'll most likely clobber you.
Done once more for Super Mario 3D Land in the special worlds. You will have a shadow clone chase you around as it follows your movements. Depending on the level, the clone will vanish as you make a transition to the next part of the level (which the clone will pop up again as you start to move on) or you can snag a Star and smash into it to temporarily disable it. Most of the time, you will have to clear the level to finally stop the clone. The last few levels in the special worlds give a giant version of the clone, making it harder to dodge it.
Mega Man sometimes must battle an exact copy of his own schematics. Given that he is an artificial construct, this is a fully justified application.
Subverted in Mega Man Powered Up. If you play as a robot master, the boss of his stage will be "Mega Man?", a clone of Rock, not the master himself.
Played straight later on in Wily's fortress.
Interestingly enough, the copies of Mega Man, despite being exactly the same, are always easily defeated by the real deal. Guess there's just no counting for experience.
Prince of Persia had you face a literal mirror copy of yourself, released from a magic mirror you had leaped through earlier. He shares your health bar, mirrors every attack identically. The only way to defeat him is to sheathe your sword.
The final boss battle of Mega Man Zero 3 is one of these, although the twist is that the boss isn't the copy, the hero is.
Tomb Raider also uses Mirror Matches, but in just a few games. In the first Tomb Raider and in the Anniversary remake, there is a skinless creature in the 2nd to last Atlantis level that has the shape of Lara Croft. The clone moves the same way Lara does and firing your guns at it hurts you, as well as the creature, so if Lara dies, the creature would too. The creature was really a puzzle where you had to trick it into falling into a trapdoor with lava below in order to move on to the next area. One level in Tomb Raider: The Last Revelation has a gold statue of Lara that hurts you if you fire your guns at it (why Lara actually aims at the thing is a mystery). Some enemies in the room actually attack the gold copy of Lara, causing harm to the real Lara.
Sonic The Fighters deals with this situation in an interesting way: If two players chose the same character, a special cutscene is shown at the beginning of the battle where Dr. Eggman flies in and shoots a ray at the first player, creating a black and white clone which is the second player.
In Sonic Battle, if more than one of the same character is selected in battle mode, each character except the original will become a version of Emerl with that character's moves and voices.
Bad/Dark Rayman from the final level of Rayman, Mr. Dark's Dare. An evil double of Rayman, Dark Rayman would literally do everything Rayman did, essentially copying the player's progress with perfect precision, albeit lagging behind by a second or two. If he touches you, you will die instantly and lose a life. Since he's invincible to any of Rayman's attacks, you are forced to keep moving throughout the entire level without allowing him to come into contact with Rayman. Successfully reaching the end of the level kills Dark Rayman, allowing you to move on.
In Shadow the Hedgehog, the two-player mode has each player controlling a clone of Shadow, with Player One as the most convincing copy.
In Vexx, some of the Wraithheart missions involve playing minigames against three clones/dark versions of Vexx, referred to as Vexx's "inner demons" in the game. The clones can be attacked and even knocked out of the arena (but they reappear a few seconds later), but only truly die when the original Vexx wins the minigame.
In Crisis Core: Final Fantasy VII, one of the Digital Mind Wave cutscenes shows Zack battling a simulation of his recorded data from last month's training, which appears as a clone of himself. The two are evenly matched - which is a bad sign, as it shows that Zack hasn't improved at all since last month.
Paper Mario has enemies that can imitate Mario or his current partner. The second game even goes as far as a boss called Doopliss fooling his partners, and the player, into thinking that he's the real Mario.
The third time you fight Doopliss, in the second battle with the Shadow Sirens, he can turn into Mario or his partner at any point in the battle.
Belome, a Recurring Boss in Super Mario RPG, is an odd-looking statue come to life. Turns out being petrified builds up quite an appetite. The second time you fight him, he will periodically swallow one of your characters and spit them out, commenting on their taste and releasing a clone. The copies have their own stats, but use "evil" versions of your techs —while Mario can toss fireballs, his copy can cause a flaming meteor to drop from the sky.
In the second expansion of the game Neverwinter Nights, Hordes of the Underdark, the player experiences a Mirror Match after looking in an actual magic mirror. However, the player also has henchmen, which tips the odds significantly in his or her favor.
It's even easier if you unequip your weapons first. The mirror opponent only fights with what you had equipped at the time you looked in the mirror, so you can re-equip your weapon while the mirror opponent can only fight with their fists.
If a player visits Umbra in Sa Ga Frontier, their trip ends with a Mirror Match between their first party and their first party's shadows.
Secret of Evermore uses this several times throughout the game. Firstly the player fights 3 different copies of himself, after which another character confusedly remarks "Wow, according to my calculations, you're at least three times stronger than yourself!". Secondly, as part of the final boss battle you must fight another clone of yourself and the computer-controlled dog that has been following you throughout the game. However, what makes it interesting is that while the clone of the player can be taken out in one shot (he's no stronger than the clones from before), the clone of the Dog has roughly 10,000 HP.
Although different characters, the duels between Luke and Asch in Tales of the Abyss otherwise fit this. Although Asch knows several spells Luke doesn't, they otherwise fight exactly the same, as they learned to fight from the same teacher. Not to mention that Luke is a clone of Asch.
As part of a test, one of the boss fights in Secret of Mana is against the Shadow Xs, dark-colored versions of the three main characters.
In Pokémon, Ditto and Mew have the move Transform, which will allow them to turn into an exact copy of the enemy Pokémon, and have all the same moves and type. But it doesn't get any stronger, meaning the original will usually win.
It's also not unusual for simply the same species to be fighting on each side. However, true mirror matches (with the exact same stats and moveset) are generally only happening in the multiplayer environment.
And the IV system (which means the chance of two Pokémon having exactly equal stats one in hundreds of millions) actually makes it almost impossible to have a perfect mirror match, especially since a Pokémon's statistics are also determined by natures and Effort Values. Further variation of each Pokémon comes in the form of differing movesets, form variations, abilities, and held items.
The main quest of The Elder Scrolls IV: Shivering Isles features one of these. You fight a (literal) shadow copy of yourself, which has all your items, powers, and skills — oh, and a big, scary sword.
With a bit of messing around with AI and status effects, the player can make someone clone them. The only downside is that it only lasts for around a minute before disappearing.
This was an engine feature implemented for Morrowind. Because of a game-crashing bug when modders tried to use it, it was forgotten until it was used again in Shivering, and now appears to be fixed.
Played somewhat straight in Final Fantasy IX, where one dungeon in the latter half of the game features actual mirrors that must be confronted, each one producing a duplicate of one of the playable characters, though not necessarily one that's actually in the active party. If the mirror character actually is duplicating someone in the party at the time, that party member receives a one-hit kill before the party can take any action (unfortunately, resurrecting that character during the fight will only cause another immediate one-hit kill from the mirror monster).
On the bright side, each mirror-monster will spawn up to three doppelgangers per battle. Defeating them grants lots of experience - you may find yourself enjoying the company for a while.
Graal The Adventure used to have a quest where the final boss was a mirror. The boss within would mirror your moves exactly. It didn't LEAVE the mirror, making it rather difficult to hit; but bombs could be thrown over the line between worlds...
Wild ARMs: Alter Code F features enemies called Doppelgangers who imitate a party member. They're just normal Mooks though. They also appear in Wild ARMs XF and will have all of the special abilities of the copied character's special class.
In Chrono TriggerDS, the Dimensional Vortex contains the Crimson Shade and Alabaster Shade, mirror opposites of Lucca and Marle, respectively. They use the same basic skills, boosted to twice their power.
Crono himself gets his own Shade, too. Interestingly enough, the doppelgangers' moves are renamed. (Luminaire becomes Scintillation, Cleave becomes Rend).
The other Shades have the same kind of renaming. (Ice II becomes Icefall, Cure 2 becomes Recuperate, Flare becomes Explosion, etc.)
Kingdom Hearts II has, at one point, a cutscene version of one of these, featuring a Nobody versus their major-character counterpart. It could've played out like a Duel Boss, except...well...it is a cutscene. At the end, said Nobody said he had a good Somebody, and he was glad to get to meet him. The fight actually is a Duel Boss in Kingdom Hearts II: Final Mix+.
Then, in Kingdom Hearts: Birth by Sleep, Terra's final boss is against his own body, with several identical moves. This is best overcome by blocking and countering all attacks directed at you. Also, Ven's final boss is Vanitas - the other half of his heart. This trope only really comes into play during the second half of the fight, though; up until then, Vanitas doesn't fight like Ven at all. And interestingly, it's Ven copying Vanitas' technique in the second half, not the other way around as you'd expect.
This happened in the first game, too, with the Anti-Sora boss fight in Neverland. Shadow Sora Heartless also appear as normal enemies in the same world. Though not strictly a mirror match, the fight against possessed Riku in Hollow Bastion feels like this, due to his similar fighting style and using dark versions of Sora's moves (such as Strike Raid).
Kingdom Hearts Re:coded features a battle against the data version of Sora's Heartless, which has transformed into an incredibly powerful Darkside thanks to absorbing the data of the other Heartless in the journal. During the fight (which is a Sequential Boss), the second, third and fourth stages have it take the form of Anti-Sora, which fights almost identically to Data-Sora.
In the prologue of Kingdom Hearts II, one of the Seven Wonders of Twilight Town has Roxas battle a shadowy version of himself, which comes out of his reflection in the waterfall.
In the Mission Mode of Kingdom Hearts: 358/2 Days, it is possible to make Xion, Saďx and Riku battle "Anti-" versions of themselves, which appear as shadow versions of the character with glowing yellow eyes (like Heartless). (Incidentally, you fight the "Anti-" version of the character no matter which character you choose for the mission, with the exception of Xion, though the Xion fight doesn't really feel like a Mirror Match since the boss is in a different form to the player character).
In The World Ends with You, the kitsune-style noise (Psychedelifox, Ambiefox, and the like) can shape-shift into other forms, usually other Noise. If they get enough tails, they can shapeshift into Neku wearing a kitsune mask, and attack you with a set pool of psychs Neku is able to equip (though not necessarily what he currently has equipped).
.hack//G.U. has this in the form of a Boss in Mook Clothing, the Doppelganger. He appears whenever you've stayed on an overworld map for too long, and is always 8 levels above you until you hit the level cap of the game (of which doing so turns him into a straight up mook), and has a unique weapon that mimics, you guessed it, protagonist Haseo's weapon that's out at the time. This means that if you have the scythe out and he finds you... Oh Crap. The fact that the game has a driving, terrifyingsynth themefor him that gets louder as he gets closer, does not help things any.
Fail to answer a sphinx' riddle correctly in Heroes of Might and Magic 5, and this will be your penalty — i.e. you have to fight an army structured EXACTLY as yours with the same creatures and led by the same hero with the same level, skills and items.
In Dragon Age: Origins there's a test during the Gauntlet in The Urn of Sacred Ashes Quest that has each party member, including the player character, face an invisible version of themselves, complete with names hovering above them and matching voices (for shouting as you kill them)
A rather interesting take is down in an early PS2 game and adaptation of Orphen called Scion of Sorcery where Orphen, Majic and Zeus are forced to fight against one. While its default form is that of a grayed out and dusty-looking version of Orphen with yellow boots, it can freely change into either of the party members. While it barely ever attacks, attacking it while it impersonates any one of you will result a significant amount of mirror damage dealt to your party but the person being imitated will receive the brunt of it and when it assumes its default form, it'll put up a barrier before launching a projectile. Reflecting the projectile with the right spell (Armor of Purity) will cause it to transform into a lizard man where it can safely be whacked on.
Mass Effect 3's Citadel DLC has the Mirror Match option in the Armax Arsenal Arena, where your opponents are clones of Commander Shepard using each of the game's six player classes. Not to mention the main antagonist of the DLC storyline, a clone of Commander Shepard using the same class and powers as the player.
Lampshaded and occasionally justified in Touhou Hisotensoku and Scarlet Weather Rhapsody, during arcade or vs mode, if the player wins a mirror match, the characters will say something akin to: "Mirror-image training completed". Marisa even says "I'm winning 101 matches out of 100 in image training!" Considering that this is Gensokyo, people creating clones of themselves for danmaku training shouldn't come of as much of a surprise.
Similarly, this is possible in the versus shooters, Phantasmagoria of Dim. Dream and Phantasmagoria of Flower View. Actually part of the plot in Dim. Dream, since the bosses don't change even if you're playing as them. Apparently Chiyuri has a Gensoukyou counterpart, and Yumemi got cloned by a device on the ship.
This can also happen, to an extent, in Imperishable Night's practice mode. In the story mode's fourth stage, you fight either Reimu or Marisa, and if you chose one of those two as your player character, you fight the other one. In practice mode, you can fight either of them with any character, including themselves. And similarly, Spellcard Practice can be done by any character, and includes bonus spellcards by playable characters.
One of Eiki Shiki's spellcards in Shoot the Bullet invokes this, forcing Aya to fight her reflection/clone.
In the less-known PlayStation game Silent Bomber, the fight with Benoit feels like this, as Benoit has exactly the same moves and equipment as the main character.
In the first Star Trek: Starfleet Command game, the player gets to fight his or her own Mirror Universe counterpart, who is flying the exact same ship. This is one of the toughest battles in the game, as tactics is the only way to win.
Mario Golf allows this, but the sequel does not. Mario Tennis only allows it in Special Games (e.g. short match) but not in the main game. This is problematic as every character plays differently, especially in the second Golf, where each character has their own power\accuracy mix, so the best players will probably all want the same one or two hard-hitters.
After unlocking Pete in Backyard Skateboarding, you can play as him in the Boardwalk; the boss challenge involves racing Pete, so you're racing yourself.
One of the bosses for Silent Hill 3 is Alessa, a carbon copy of the protagonist Heather, only decaying and bloody.
Part of the lead-up to the final boss in the NES game Sweet Home features a number of one-on-one fights against mirrors of your own five-member party. Since there are two or three paths to the final boss platform, which path you take indicates which party member double(s) you have to fight.
Joining the ranks of Nintendo Dark Doppelgangers is Dark Pit in Kid Icarus: Uprising. He has all the same gameplay limitations as Pit note the actual boss fight has an exception, as he constantly takes to the air and starts spamming Rain of Arrows, and if you know what he's gonna bring to any given battle, you can equip Pit thusly and make it a true Mirror Match. Can't say the same for his stats, though.
Parodied, somewhat, when Fighter splits up the Light Warriors, Dark Warriors, and Other Warriors into new teams. Fighter places himself on every team (in one case, three times). Thief convinces Fighter that he's picked a "random" representative from each team to have a fight to the death (naturally, he picked each team's Fighter), leaving a very confused Fighter fighting "himself"... but there's still really only one of him, so he stoically waits for an attack to counter, leaving him frozen in place for a while.
Goblins has a variation; the dungeon the Maze of Many forms a link between all the dimensions in the multiverse,and pits adventuring parties against versions of themselves from all possible realities. It's not a straight mirror match, though, since there are subtle differences between each individual, depending on which reality they originated in.
Dragon Ball Multiverse: One of the chapters has U16 and U18 Gotenks fighting each other, thus causing this trope to be in play. And boy, is it played to the hilt, as the two do the exact same things. So much that when they inevitably defuse, one of the halves has to ask which of the two other fighters is from his Universe. One of them just gives up.
In an episode of the Aladdin TV series, Chaos makes an evil copy of Aladdin. The hero wins by using his evil counterpart's lamp to wish him away. The "evil" Aladdin didn't free his genie as the real Aladdin did.
Things went a little differently in the comic book version of the story. All the Titans except Raven (who was turned into a demon and on her father's side), Jericho (who was badly injured), and Lilith (a wild card) were forced into nightmare scenes by Trigon where they had to fight their evil clones (Cyborg's copy was fully human but just as strong, stole his girlfriend, and made the disabled kids Cyborg befriended turn against him). All of them, even Nightwing and Beast Boy, killed their copies and their souls were forfeit to Trigon as a result. Unfortunately for Trigon, this didn't convert them to his side as intended and simply made their methods more ruthless. They killed Raven, which turned out to be part of Lilith and the goddess Azar's plan to stop Trigon (Raven got better...eventually).
In the Futurama episode "The Farnsworth Parabox", the gang enter an Alternate Universe and the two Leelas start fighting. But because their moves are identical, they both knock each other out after the first hit.
Prof. Farnsworth: Now, now. Perfectly symmetrical violence never solved anything.
When Captain America finally gets to face off against his Skrull doppelganger in The Avengers: Earth's Mightiest Heroes, it goes down like this, though the Skrull Cap was already transformed and looks like an alien wearing the Captain America suit rather than a direct mirror image of the Star-Spangled Avenger. Cap is more than a match for his double and defeats him in a most satisfyingmanner.
The episode in which Skrull impersonators of the first eight Avengers try to invade Wakanda has Black Panther, Wasp, and Hawkeye each fight alien versions of themselves. The real Black Panther and Hawkeye each kill their alien counterparts, while Wasp's becomes defeated by Hawkeye. The other Skrulls have to settle for fighting Avengers that they aren't copying.
Another episode features the Avengers dealing with robotic copies created by Ultron. Two notable scenes in the episode include a direct example of this trope: One with Hawkeye and Cap dealing with their robot doubles at Avengers Mansion, and later at the climax when the assembled Avengers team take on the entire team of robot Avengers (save for the Captain America double, who had been destroyed in the former battle at the Mansion.).
In Space Stars, Space Ghost ends up fighting his evil Mirror Universe counterpart Space Spectre. They wind up evenly matched, but then Jan, Jace, and Blip attack Space Spectre, the distraction allowing Space Ghost to defeat him. Space Ghost quips, "I have friends. You don't."
Aku once created a clone of Samurai Jack from his negative emotions. They were evenly matched until Jack cleansed himself of all negative emotions, destroying the clone.
In Transformers Prime, human terrorist organization, MECH, ultimately succeeds in creating a robot drone with all of Optimus Prime's abilities and strengths that defeats all the other Autobots and manages to fight Optimus on equal footing. He is ultimately defeated when one of the Autobot's human allies distracts the drone's operator.
Megatron of Beast Wars was able to create a clone of Dinobot with the original's personality and memories, but an inability to transform. The real Dinobot and the clone battled with former opting to remain in beast mode to keep the match fair. The original ultimately defeats and eats the clone remarking that he was quite tasty.