A form of NamesToRunAwayFromReallyFast: Some people end up going by a pseudonym where they have a one-word description followed by an X. It's generally not a good idea to press them for real names.

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!!Examples:

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[[folder: Anime & Manga ]]

* ''Manga/OnePiece'' has an inverted example in X Drake (though the X is pronounced "Diez", as in [[GratuitousSpanish the Spanish equivalent of "10"]], [[BilingualBonus which "X" is the Roman numeral for]]).
* The titular mech from ''Anime/AfterWarGundamX'' also counts.

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[[folder: Comic Books ]]

* Marvel Comics, who publish ''Comicbook/{{X-Men}}'', has Professor X, Weapon X, Agent X, and Mutant X.
** {{X-23}} is an OppositeSexClone of {{Wolverine}} (aka "Weapon X") who has been trained as an assassin since basically birth.

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[[folder: Film ]]

* From ''Film/GodzillaFinalWars'', we have the last monster Franchise/{{Godzilla}} fights, named Monster X. Unlike the other {{kaiju}} in this film, Monster X puts up a great fight. [[spoiler:...And then he turns into [[Main/OneWingedAngel Kaizer]] [[Main/OhCrap Ghidorah]] and [[Main/CurbstompBattle turns the tide of the battle in his favor...]]]]

[[/folder]]

[[folder: Live-Action TV ]]

* ''Series/CSINewYork'' had a storyline about a female ProfessionalKiller who they only referred to as "Suspect X." Her crimes included killing an Internet celebrity to take her identity, assassinating a federal judge, holding hostage, surgically altering and finally killing a random innocent woman to fake her own death, and [[ArsonMurderAndJaywalking hacking Second Life.]]

[[/folder]]

[[folder: Video Games ]]

* While ''VideoGame/MegaManX'' himself is a [[TheHero heavy]] {{aver|tedTrope}}sion in the games proper, he does have an evil counterpart from the Megamission card game, "Mega Man iX". And then there's [[VideoGame/MegaManZero Copy-X]] to consider...
* Longshoreman X (yes, really) is a boss in the original ''VideoGame/DeadToRights''. He fights with full fisherman gear and a spear gun.
* In ''VideoGame/CaveStory'', an infamous boss is called Monster X.
* In ''VideoGame/KingdomHeartsII'', the only real "boss" in the Gummy Ship Missions is called Hunter X, found only in the very last mission on the hardest difficulty.

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[[folder: Web Original ]]

* ''GaiaOnline'' has Labtech X.


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[[folder: Western Animation ]]

* Red X; not just the only ''antihero'' in the series but also the only character to never be defeated! (from the animated ''WesternAnimation/TeenTitans'', with a ''color'' to boot!)
* ''WesternAnimation/BeastWars'' gives us Protoform X, complete with a big ugly X on his stasis pod. Becomes the aptly named Predacon Rampage once he's released.

[[/folder]]

[[folder: Real Life ]]

* Malcolm X, why not. Real life BadassPreacher extraordinaire, not to mention (at least from his own perspective) an epic HeelFaceTurn when he left the black separatist Nation of Islam for mainstream Islam.
* There is an as of yet unidentified pliosaur known as Predator X. Estimates put its length at about 50 feet and give it a bite force more powerful then a TyrannosaurusRex.
* Planet X
* Angelspit's DestroyX.
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