[[quoteright:189:[[UsefulNotes/MacOS http://static.tvtropes.org/pmwiki/pub/images/OSXLeopard.png]]]]
[[caption-width-right:189:This is the coolest letter in the world. [[TheInternetIsForPorn Especially in triplicate]].]]

->'''Leela:''' You're blackmailing me?
->'''Bender:''' [[BlackmailIsSuchAnUglyWord 'Blackmail' is such an ugly word]]. I prefer 'extortion'. The 'X' makes it sound cool.
-->-- ''WesternAnimation/{{Futurama}}'', "Anthology of Interest I"

There's always something about the letter X that just makes anything cool (including this article). A lot of people use it gratuitously on a name, product, model, etc. just so it has some sort of edge to it. Want some pizzazz? Add an X somewhere in the name. It doesn't matter where, as long as there's an X. And it has to be a capital X. Lowercase x is just too puny to be cool. [[AccidentalInnuendo Just don't add 3.]]

In order for this trope to work, though:
* The product isn't the 10th installment of a series that already used Roman numerals.
** On the other hand, if the series goes 1, 2, 3, 4, 5, 6, 7, 8, 9, X...
* The X doesn't stand for a multiple of something. Example would be AMD's line of Athlon and Phenom processors: Athlon X2, Phenom X3, Phenom X4, etc, which don't count because the X indicates how much cores the CPU has; on the other hand, the FX line and the overclockable Ryzens that have an X after the model number do count.
* There's no real justification to use the X. Another letter would easily work if the X was a part of a word.
* If it's in the designation of a vehicle or other object, it can't be a prototype. In such cases it stands for e'''x'''perimental, and gets changed or removed when it enters full production.
** Though it ''does'' add that extra bit of coolness to a SuperPrototype, we admit.
* Similar to the above, the ''X'' in question is used as an abbreviation in an acronym for a word in English that has the ''ex-'' prefix, which would properly use ''E'', but ''X'' looks cooler, of course. (Only a few English words begin with X, and most of those derive from Greek. The same holds for most European languages.)

Subtrope of XtremeKoolLetterz. For tropes that make use of this and when a work sequel adds the ''X'' after the original title, see LetteredSequel. See also FourX, LetXBeTheUnknown. Not to be confused with [[SugarWiki/AndTheFandomRejoiced [A Metasyntactic Variable As Portrayed In This Case By X] Makes Anything Cool]].


[[folder:Anime and Manga X]]
* ''Anime/SpeedRacer'' has Racer X. And [[WesternAnimation/SpeedRacerTheNextGeneration later named a child "X"]].
* ''Anime/SonicX'', but we all know that Sonic is cool anyway.
* ''Manga/{{X1999}}'', an anime made by Creator/{{CLAMP}}. Then they went overboard and became ''Manga/XxxHolic''... (The xxx is silent, it denotes a variable in Japanese. The English would be ___holic.)
* The working title for ''Anime/{{Pokemon 2000}}'' movie was Pokémon X, and in fact there is a faint X shape in the final version poster/cover of the Japanese version.
** That explains why Lugia is referred to as 'Mystery Pokémon X' in a Johto miniarc.
* ''[[Anime/AfterWarGundamX Gundam X]]'', though it didn't ''quite'' work...
** Justified, though, in that the titular Gundam's wing binders open up in the shape of an X when it deploys its [[WaveMotionGun Satellite Cannon]].
* ''Anime/TurnAGundam'' gives us the Turn-X Gundam. Whose name doesn't make a lick of sense, but the thing is awesome ''and'' deadly!
* The ''Franchise/LyricalNanoha'' franchise gave us ''Audioplay/StrikerSSoundStageX''. Confused some people into thinking that this was the tenth Sound Stage (it was the eleventh, excluding the [[FourthWallMailSlot Megami Sound Stages]]). The X [[OneLetterName stood for the]] MysteriousWaif.
* The titular character from ''Anime/BtX'' is a mechanical kirin, famous for being the most powerful battler of the villainous [[TheEmpire Machine Empire]]. Fortunately, he decides to [[HeelFaceTurn help the hero]]...
* While they haven't yet appeared in the show, the ''TabletopGame/YuGiOh'' card game has the X-Sabers and their beefed-up cousins, the XX-Sabers. [[GettingCrapPastTheRadar I hate to see what they do with the]] ''[[DoubleEntendre third]]'' [[InnocentInnuendo installment of the monster series]].
** Also the most probable reason for 4Kids deciding to pronounce the previously silent X in ''Anime/YuGiOhZEXAL''
* ''Manga/CannonGodExaxxion'' has not one, but three Xs. They explain later that the XXX marks that are stamped all over the title [[SuperRobot robot]] aren't really Xs at all, but rather the last letter of the alphabet used by the aliens who created it. XXX is their generic symbol for an antimatter reactor, as the letter has similar connotations to the Greek letter Omega.
* Planet X in ''Anime/TransformersCybertron''.
* The GirlsLove manga ''Manga/HayateCrossBlade'' (where the X is pronounced "cross".)
* ''Manga/{{Bleach}}'' deals with an organization called Xcution.
** Lille Barro of the Vandenreich has an ability called "The X-Axis", one of the most powerful abilities seen among the Schrift and outside of it, and he is an expert sniper with heavy angel motifs.
* ''Anime/RomeoXJuliet'', where the X is still intended to be pronounced "[[RomeoAndJuliet and]]".
* ''Anime/RahXephon''.
* This is the basis behind the name of X-Brawn in ''Anime/TransformersRobotsInDisguise''. It was for a whole thought that X-Brawn was used because Hasbro couldn't secure a trademark on 'Brawn', but one of their marketers later explained that they just put in the X too look cool.
* ''Manga/MysteriousGirlfriendX''. Extra-strange because the X doesn't seem to mean anything (the "mysterious girlfriend" has an actual name).
* The anime adaptation of ''Manga/RurouniKenshin'' has two english dubs. One of them leaves the title unchanged, while the other renames the show "Samurai X".
* Halfway through ''Anime/DigimonAdventure02'', the main hero Digimon, V-mon (Veemon), finally gets a proper digivolved form of his own, a giant buffed version of himself called XV-mon ([=ExVeemon=]).

[[folder:Comic Books X]]
* ''Franchise/XMen''. Because ex-men just doesn't sound cool enough.
** But for some reason, ''Ex-Mutants'' was...or maybe not.
** Creator/StanLee wanted to call it "The Mutants," but ExecutiveMeddling (this was TheSixties, he wasn't an executive yet) prevailed. He was told that nobody would know what a mutant was. "But they ''would'' know what an "X-Man" is?" fell on deaf ears.
** X-Men spinoffs have driven this so far into the ground it's punched right through the planet.
*** ''[=X-Treme X-Men=]'' being the ultimate offender.
*** Not to mention peripheral X-character "Adam X the X-Treme." Created in the heyday of the NinetiesAntiHero, he has ''that'' name and the power to [[DarkerAndEdgier ignite people's blood]] and possesses more spikes than [[SpikesOfVillainy actual bad guys]] on his costume in order to expose said blood to the air. Top it all off with a baseball cap worn backwards! Basically the living definition of "trying too hard." (Last seen setting TheJuggernaut [[KillItWithFire on fire,]] and then [[OhCrap realizing that]] he'd set [[NighInvulnerable the Juggernaut]] [[WreathedInFlames on]] [[InfernalRetaliation fire.]] Yeah, ''that'' coulda gone better.)
* ComicBook/{{Wolverine}} has a villain called Mister X.
** And of course Wolverine is Weapon X. (These days, it's the Roman numeral, making him the tenth ''weapon'' created by the SuperSoldier project. ComicBook/CaptainAmerica is Weapon I. But that's a retcon created recently in the scheme of things.)
* Moira [=Mac=]Taggert's prisoner, the mysterious Mutant X, who turned out to be [[spoiler: her son, AKA Proteus.]] The name was dusted off in the '90s for the comic book starring Havok trapped in a ParallelUniverse, and an unrelated TV series Marvel had ''some'' hand in (''Series/{{Alphas}}'' is sort of a SpiritualSuccessor).
* The ComicBook/GuardiansOfTheGalaxy's Groot comes from Planet X. He was invented in Marvel's 1950's monster comics, where the name "Planet X" was actually recycled a few times, but the name seems to have stuck in his case.
* Comic artist Frank Granados goes as "Franx Granados" (or just "Franx").

[[folder: Fan Works X]]
* ''Literature/HarryPotter'' {{Fanfic}} ''Fanfic/MyImmortal'' features goffik band [=XBlakXTearX=], featuring Serious Blak, Snap, Lucian Malfoy, and Jamez "Samoro" Potter. Notable for the fact that the latter once [[DisproportionateRetribution shot Lucan's arm off for playing a song wrong.]]
* ''Fanfic/PaperMarioX.'' The X stands for {{crossover}}.
* One of the most popular ''Franchise/SuperMarioBros'' fangames has the title ''VideoGame/SuperMarioBrosX''. After the original URL where the game was located, supermariobros.org, was purchased by Nintendo, the creators were able to get away with it by adding an X to it ([[http://supermariobrosx.org supermariobrosx.org]]), also invoking this trope.

[[folder:Film X]]
* The former MPAA rating X, now essentially synonymous with pornography.
** "XXX", a porn industry marketing gimmick intended to imply something along the lines of [[RuleOfThree "this movie is three times raunchier than an ordinary X"]].
** And the [[http://www.theonion.com/content/node/29713 less-desirable XX]].
* ''Film/XXx'', starring Creator/VinDiesel. xXx's real name is Xander Cage, so the xXx tattooed on his neck could be his initial [[RuleOfThree repeated three times]]. However, after he steals an [[MoralGuardians anti-game senator's]] sports car and drives it off a bridge so he can BASE jump off it in the opening scenes, Creator/SamuelLJackson's character suggests the three X's could also mean three "strikes" against the law.
* X-Wings in ''Franchise/StarWars'' are, like other crafts of the Rebel Alliance, named so because they look like that letter. This is interesting because the ''Star Wars'' universe uses the [[http://starwars.wikia.com/wiki/Aurebesh Aurebesh]] script, leading to the question why inhabitants of a galaxy "far, far away" should name their ships after Latin letters. TranslationConvention, or just more InexplicableCulturalTies? Eventually it's {{retcon}}ned that a "[[http://starwars.wikia.com/wiki/High_Galactic_alphabet High Galactic]]" script that's [[InexplicableCulturalTies inexplicably identical to the Latin alphabet]] also exists in the ''Star Wars'' universe.
* ''Film/TheLeagueOfExtraordinaryGentlemen'' FilmOfTheBook is acronymed LXG. Why? Just because.
* Advertisements for ''Film/MalcolmX'' often featured simply a lone "X" logo. This actually backfired a bit on them because you cannot trademark a letter, so the filmmakers could not claim a cut from knock-off merchandise.
* The spacecraft Zero-X in the first ''Series/{{Thunderbirds}}'' film, ''Thunderbirds Are GO.'' Not a prototype, this was the one intended for the first trip to Mars, [[spoiler:until it failed during liftoff and [[StuffBlowingUp exploded in the ocean]]]]. The replacement ship that launched two years later (2067) was also called Zero-X.
** In the backstory of ''Series/CaptainScarletAndTheMysterons'', a third Zero-X mission was launched in 2068 ([[spoiler:the second Zero-X also exploded]]), suggesting that the name refers to the spacecraft design, as well as with the [[spoiler:only extant]] ship.
* ''Film/JasonX'', which also just happened to be the tenth movie in the ''Franchise/FridayThe13th'' series.
* In the remake of ''Film/TheLongestYard'', Joey Battle (played by Bill Goldberg) has "X" as his uniform "number".

[[folder:Literature X]]
* Agnes Nitt, a young woman in the Literature/{{Discworld}} novels, desperately tries to acquire some cool by (briefly) assuming the name [[AwesomeMcCoolname Perdita X Dream]], where [[MysteriousMiddleInitial "X"]] stands for "someone who has a cool and exciting middle name." Doesn't work though -- all the people in her village refer to her as "the Agnes who calls herself Perditax."
** In ''Discworld/UnseenAcademicals'', we find that Dr. Hicks, the head of [[InsistentTerminology Post-Mortem Communications]] at Unseen University first introduced in ''Discworld/MakingMoney'', has started spelling his last name Hix because "a man who wears a [[GoodColorsEvilColors black]] robe with nasty symbols on it and has a skull ring would be mad, or let us say even madder, to pass up the chance to have an X in his name."
** Discworld also features the continent [[LandDownUnder XXXX]]; this was originally a mapmaker's label, as in it was so unknown they didn't even know what a good name was for it. "Fourecks" actually ''became'' its name.
*** XXXX is also the name of [[https://en.wikipedia.org/wiki/Castlemaine_XXXX a well known Australian beer]], pronounced Fourecks.
* In Craig Charles' ''The Log'', he advises any heroes in a movie, when confronted with the villain's office full of filing cabinets, to go straight for the one labelled 'X'. "No evil mastermind has ever named his plan to TakeOverTheWorld 'Project W', guys."
* The [[TheHeartless Echthroi]] in Creator/MadeleineLEngle's book ''Literature/AWindInTheDoor'' have the power to unmake elements of creation, a process referred to as Xing.
* ''Literature/DanielX''
* In Literature/ThePendragonAdventure, the biggest competition in Quillain's existence is the Grand X.
* The SF trilogy by Ramez Naam: "Nexus", "Crux", "Apex". The second one even got a somewhat shoehorned TitleDrop in the respective book, as if to say: [[SarcasmMode "Hey, it's totally NOT this trope!"]]

[[folder:Live Action TV X]]
* ''Series/GameOfThrones'':
** The Boltons seem to think so and this includes desecrated corpses! The saltire motif is prominently displayed on Bolton heraldry and paraphernalia, and represents the Saint Andrew's Cross-like torture frame that they bind their victims to. Even the Bolton forces' little figurine on Robb Stark's map has the screaming flayed man on an X-frame.
** House Umber's sigil is four chains linked by a central ring on a dark red field.
* The TV show ''[[ShowWithinAShow Wormhole X-Treme!]]'' within ''Series/StargateSG1''.
-->'''Martin''': Research says that shows with "X" in the name get higher ratings.
* [[Franchise/StarTrek Starfleet]] designates experimental starships' line number with NX, instead of the usual NCC. Unfortunately, NX is changed to NCC as soon as the model enters common use.
** In ''Series/StarTrekEnterprise'', the "NX" designation is used for the entire class of starships that the ''Enerprise'' belongs to, as the Earth Starfleet operates under different conventions than the chronologically later series' Federation Starfleet.
** Every proper noun in the language of [[Series/StarTrekVoyager Neelix's]] species, the Talaxians, contains an X somewhere.
* In ''Series/KaizokuSentaiGokaiger'', the TransformationSequence includes three [=Xs=] (and a V) because ''Gokaiger'' is the 35th Franchise/SuperSentai series.
* ''Creator/DisneyXD'', or "eXtremely Digital". That's right, little boys, [[WereStillRelevantDammit Disney is cool now and totally not just for girls]].
* ''Series/MostExtremeEliminationChallenge'' or just MXC. Don't get eliminated!
* ''Series/TheXFiles'':
** The famous FBI department is called simply X-Files for no apparent reason. However, there is a really cool explanation which appeared on the show in season 5. They might have been called the U-Files for "unsolved" but weren't thanks to the filing system at the FBI in the 50's.
--->'''Clerk Bahnsen:''' It's in an X-file.
--->'''Agent Dales:''' An "X-file"?
--->'''Clerk Bahnsen:''' Yes, unsolved cases. I file them under "X".
--->'''Agent Dales:''' Why don't you file them under "U" for "unsolved"?
--->'''Clerk Bahnsen:''' That's what I did until I ran out of room. Plenty of room in the "X"s.
** Agent Mulder's second MysteriousInformant is known only as Mr. X.
* Franchise/{{Kamen Rider}}s [[Series/KamenRiderX X]], [[Film/KamenRiderZX ZX]], and [[Series/KamenRiderBlackRX Black RX]].
* ''Series/UltramanX'' puts the X on whatever it can find. Heck, the Xio team HomeBase is a giant building shaped like an X!

[[folder:Music X]]
* Music/XJapan was originally just named just X. They changed their name when they gained international recognition because there was already a punk band in the USA called X.
** In the opposite direction, for a few years in the 1990s British band Bush was known as Bush X in Canada, because a Canadian band from the 1970s still owned the name there.
** British group Liberty X added their X for similar reasons, after being formed from a TV talent show's runners-up as plain 'Liberty'. This was a permanent change, though, as the name was contested within the UK, rather than being a monicker-of-convenience temporarily adopted abroad.
* Progressive metal group Music/SymphonyX.
* Brand X.
* Rapper and sometimes Riddick-antagonist Xzibit.
** Don't overlook his signature song that goes "'''''X!''''' (untz-untz-untzuntz) '''''X!''''' (untz-cont'd)". Snoop Dogg is also featured in the ending:
--->Mr. X-uberant, X-travagant, X-traordinary, X-citing, X-alotta.
--->And what's the recipe? X-calibur weaponry, and we shoot them X-ceptionally.
--->X marks the spot? Fuck not, X spots the marks. X-clamation point, niggas.
* Music/TheXX, who also was originally named X before realizing that there were other bands with that name.
* HardcorePunk and [[{{Metalcore}} Metallic Hardcore]] bands (particularly those of the UsefulNotes/StraightEdge persuasion): X's drawn or tattooed on hands are common fashion and often incorporated into band names as well (examples include xDeathstarx, xTyrantx and xLooking Forwardx).
* The ur-example is Los Angeles punk band X, led by John Doe and E'''x'''ene Cervenka.
** And the Australian band with [[NamesTheSame the same name]].
* Gibson Guitar Corporation created the [[BrokenBase mixedly-received]] [[http://www2.gibson.com/Products/Electric-Guitars/Firebird/Gibson-USA/Firebird-X.aspx Firebird X]], an electric guitar with digital effects and other futuristic additions. Granted, the previous Firebird models are defined with roman numerals (Firebird I, II, III, V, VII and XII) but there never was a VI, VIII or IX. Neither was there XI making the XII and X most probably this trope..
* {{Industrial}} and [[ElectronicMusic EBM]] bands are fond of this trope. We have X-RX, X-Fusion (and [[BackwardsName Noisuf-X]]), Studio-X, [=XP8=], H.E.X.E., among others. Even bands that don't strictly fit this trope still make frequent use of XtremeKoolLetterz.
* Borderline case: Charlie Sexton's 2nd album, titled just "Charlie Sexton", with the "X" of his name red and x-tra large. Hey, theoretically he could have used any ''other'' letter than the X for that purpose, so it falls under this trope...
* Music/{{XTC}}. Doubles, of course, as a {{Pun}} [[DontExplainTheJoke on ecstasy]].
* Progressive rock band Twelfth Night's 1986 album is sometimes listed as ''X'', but that's actually a mistake. The cover features the band's name incorporated into what looks like a double-underlined X, but is actually the Roman numeral XII (for Twelfth) on its side. The album's actually called [[SelfTitledAlbum Twelfth Night]].
* For Music/{{Pentatonix}}, the group was originally going to be called "The Pentatonics;" after the pentatonic scale. A friend suggested dropping the "The" and adding X at the end.

[[folder:Pinball X]]
* Creator/SternPinball's ''Pinball/StrikerXtreme'' combines this with TotallyRadical.

[[folder:Professional Wrestling X]]
* The seventeenth and eighteenth Wrestling/{{WrestleMania}}s, called, respectively, [[http://en.wikipedia.org/wiki/WrestleMania_X-Seven WrestleMania X-Seven]] and [[http://en.wikipedia.org/wiki/WrestleMania_X8 WrestleMania X8]].
* Then there was "X-Pac," though it wasn't clear what his name was supposed to mean.
* And short-lived, Creator/{{MTV}}-backed promotion Wrestling Society X.
* Wrestling/DGenerationX
* Werewaling/{{TNA}}'s X-Division, the Ultimate X match, and the pay per view Destination X.
* No better way to exemplify the trope than Wrestling/VinceRusso's early TNA stable "Sports Entertainment [[XtremeKoolLetterz Xtreme]]"[[note]]Which obviously stands for [[MostWritersAreMale something rather low-brow[[/note]]

[[folder:Radio X]]
* ''Radio/OurMissBrooks'': "Project X" in the episode of the same name.
* ''Radio/DimensionX'' and ''Radio/XMinusOne'', two related ScienceFiction [[GenreAnthology anthologies]] from TheFifties.
* There was a Sci-Fi episode of a radio drama called "Project X" about Martians.

[[folder:Video Games X]]
* The UsefulNotes/{{Xbox}} line of game consoles is the highest profile example in all of video gaming. Its ancestor, the 8-bit MSX computer line, invoked this trope all the way back in the 1980s. Apparently the single X lost its luster, though, so they [[SequelEscalation added another one]] for the 2017 edition, the "Xbox One X."
* ''VideoGame/MegaManX''. This may have caused confusion, as the American release used Roman Numerals to denote the title while Japan used Arabic numbers. So to Japan, ''Mega Man X'' was just a name. To Americans, they might have thought this was the tenth Mega Man game (though this was {{Jossed}} long before the release of ''VideoGame/MegaMan10'').
** ''WebVideo/TheAngryVideoGameNerd'' mentioned it in his name confusion video.
** Even ''Webcomic/PennyArcade'' [[http://www.penny-arcade.com/comic/2006/02/24/ got it mixed up]].
** A later series goes even further: ''VideoGame/MegaManZX'', it's very convenient that the characters Zero and X already have the naming conventions to set up the kool title.
* ''X-Blades'', for no real reason.
** Originally called ''Oniblade'', which would make this a case of [[{{Animesque}} Anime Makes Anything Cool.]]
* ''VideoGame/DanceDanceRevolution'' recently joined in the group of games with an X: ''Dance Dance Revolution X''. Although there is some meaning to it as it was released during the game's tenth anniversary.
** Some of the MAX series of songs like to throw in an extra X: MaxX Unlimited, Fascination MAXX, and the supposed dummied song MAX to the XXXimum.
** Not to be confused, of course, with ''VideoGame/RevolutionX'', the only UsefulNotes/ArcadeGame to run on Creator/{{Midway|Games}}'s "X-unit" board.
* ''VideoGame/MetalSlug X'' and ''Metal Slug XX'', which were remakes of ''Metal Slug 2'' and ''Metal Slug 7''.
* ''VideoGame/MicrosoftFlightSimulator X'', the tenth game in the series. All previous ''Flight Simulator'' games were named after the year they were released.
* ''[[VideoGame/SuperSmashBros Super Smash Bros Brawl]]'' is titled ''Dairantou! Smash Bros X'' in Japan. ''Melee'' was also ''DX'', short for [=DeluXe=].
* Thanks to [[{{Bowdlerise}} censorship]] in ''VideoGame/FinalFantasyI'' on the NES, Kill was named XXXX. There's also the Warp/Banish spell, occasionally known as X-Zone as in ''VideoGame/FinalFantasyVI''.
** On the subject of the Final Fantasy series, ''[[VideoGame/FinalFantasyX2 Final Fantasy X-2 ]]'' probably counts as an aversion, as the X still stands for "ten", the game that ''X-2'' is a direct sequel to. Yes, this means there are two layers of numbering on this game; what's your point?
* ''VideoGame/GuiltyGear X'', ''XX'' and ''Xrd'' (apparently pronounced "Zex", "Igzex" and "Igzurd", respectively.)
* ''VideoGame/PaperMarioTheThousandYearDoor'' has the X-Nauts.
** And the X-Yux (supposedly pronounced "cross-yux"). Or just the Yux in general.
* ''[[VideoGame/PokemonColosseum Pokémon XD]]'', even if it is a MeaningfulName. And there's ''[[VideoGame/PokemonXandY Pokémon X Version]]'', which comes with ''Pokémon Y Version''.
* In ''VideoGame/{{Metroid}} Fusion'', the alien baddies were named 'X'. These were so Badass, the old ones had to create a bioweapon to stop it, which was then stolen and used to terrorize the galaxy.
* FourX strategy games. They should actually be Four E strategy games, but ''X'' is cooler.
* The ''Franchise/KingdomHearts'' series ''loves'' this, overlapping with LetXBeTheUnknown:
** Every member of Organization XIII has an X in their names in a form of ThemeNaming -- their names are anagrams of their original names, plus an X. Some of these work fairly well like Dilan becoming Xaldin, but some like Axel just seemed to raise questions and eyebrows. [[spoiler: Even when his real name was revealed to be the slightly feminine looking Lea (pronounced Lee to mitigate that) in 358/2 Days.]] The exception is Xemnas, who stole the name Ansem before his transformation. His original self was named Xehanort, which, if the X is removed, can make "no heart" and "another" - or [[spoiler: "no earth", given he steals the body of a guy named Terra.]]
*** ''[[VideoGame/KingdomHeartsDreamDropDistance Dream Drop Distance]]'' reveals that [[spoiler:the X is formally known as the "Recusant's Sigil" - a mark that gives Xehanort the ability to seek down anyone marked with it. Naminé, who is exempt from the ThemeNaming, manages to stay out of their reach.]]
** There's also the χ-blade from ''VideoGame/KingdomHeartsBirthBySleep''. It's spelled like the actual Greek letter "khi"(or chi), which makes it a MultipleReferencePun and is the reason for the Organization's naming practices mentioned above. And its wielder can fire a SwordBeam, of course in the shape of an X.
* The Japan-only UsefulNotes/GameBoy game ''X'' and its [=DSiWare=] sequel [[http://www.youtube.com/watch?v=7lfPZ75XcpQ X-Scape]]
* The UsefulNotes/DSiWare game ''VideoGame/PhotoDojo'', known as ''Photo Fighter X'' in Japan.
* In ''VideoGame/{{Xenosaga}}'', the character KOS-MOS (she's a robot... imagine that) has a development code of KP-X.
* The Japanese version of ''[[VideoGame/StreetFighter Super Street Fighter II Turbo]]'' is called ''Super Street Fighter II X'' (likely changed due to the fact that the letter X could be confused with the roman numeral for ten). This is the reason why the letter "X" appears when a Super Combo is used in the UsefulNotes/GameBoyAdvance version, as well as why the "Super Turbo"-like fighting style in ''Street Fighter Alpha 3'' is called "X-ism".
* ''VideoGame/CommandAndConquer: The First Decade'' has an X superimposed in the box art. Of course, it makes sense, but you know....
* Early 90s arcade shooter ''Xexex'', which also has the benefit of being a palindrome.
* The final boss music from ''VideoGame/{{Touhou}}'' Hisoutensoku is Unknown X, Unfound Adventure.
* When [[VisualNovel/PhoenixWrightAceAttorney Phoenix Wright]] gets a cold, his favorite brand of cold medicine is called Cold Killer X. Note, this only applies to the localization. In the original Japanese version, it was called Cold Killer ''Z''.
* Creator/DanielRemar likes to use the Roman "X" instead of "10" in his games (such as ''VideoGame/{{Iji}}'') for this reason.
* The UsefulNotes/SegaGenesis CDX was an all-in-one console that could play both cartridge and CD games, and also served as a (not very) portable audio CD player. The Genesis also had the 32X add-on.
* The early online adapter for the Genesis and the SNES, the UsefulNotes/{{XBAND}}.
* In the mid-90s, a reader of ''Electronic Gaming Monthly'' who noticed this phenomenon wrote a letter to the editors asking what the deal was. EGM responded with a sarcastic, dismissive remark, because at the time, EGM responded to ''every'' letter with a sarcastic, dismissive remark.
* Before its release, the code name of the first UsefulNotes/PlayStation was PS-X, short for [=PlayStation=]-eXperimental. Later, Sony released a digital video recorder with integrated Playstation and UsefulNotes/PlayStation2 hardware, called PSX.
* The PSX...err, ''[=PS1=]'' games ''1Xtreme'' (originally titled ''ESPN Extreme Games''), ''2Xtreme'', and ''3Xtreme''. Supposedly they are a combination of racing and eXtreme sports, as in rollerblades and skateboards.
* [[VideoGame/GrandTheftAutoIV Playboy X]]
* ''VideoGame/XCom''. It stands for "eXtraterrestial [=COMbat=] unit". And sounds extremely cool.
* Egosoft's [[VideoGame/{{X}} X-Universe]], an entire series which gets its name from the player's ship in ''X: Beyond the Frontier'': The Xperimental Shuttle.
* The tenth ''Franchise/MortalKombat'' game is called "''VideoGame/MortalKombatX''" (which is "ex" as in "next"...[[DoubleMeaningTitle but also "10"]]).
* The sequel to ''VideoGame/{{Xenoblade}}'' is entitled ''Xenoblade X''. No explanation has yet been given for the X in the title, though until recently the codename for the game was just "X" before it was revealed to be a ''Xenoblade'' sequel.
* ''Klaxxon'', so cool they x-ed it twice. (If not it wouldn't have been an example. In this case, the X is somewhat justified - can you imagine the game being titled "Horn" or "Siren"? - because you get extra points for making a big X in gameplay.)
* Some skills in the ''Franchise/{{Disgaea}}'' series have X-shaped [[AreaOfEffect areas of effect]].

[[folder:WebAnimation X]]
* Xeriouxly Forxe, the mock-DarkerAndEdgier version of ''WebAnimation/HomestarRunner'' has a loose system for it: Generally, any 'S' sound is replaced with an X. The characterx have acknowledged the difficulty of xpeaking thix way.

[[folder:Webcomics X]]
* ''Webcomic/{{xkcd}}''. According to WordOfGod, it doesn't stand for anything, it's chosen to make it difficult to pronounce, and of course because it's cool. And yes, its official spelling is with all lowercase, or possibly all uppercase if that is not usable for some reason. Xkcd is "frowned upon".
* Well, [[BigBad Xykon]] from ''Webcomic/TheOrderOfTheStick'' certainly thinks so. He chose the name Xykon for himself after meeting a man named [[LawyerFriendlyCameo Xavion who wanted to recruit him]] for [[ComicBook/XMen his team of sorcerers]], and thought the name "Xavion" sounded cool.
* In ''Webcomic/CharbyTheVampirate'' Dr. Hayter left the Blackbox project for the mysterious Project X shortly before Menulis ate the two scientists he'd been working with on the project during a full moon.

[[folder:WebOriginal X]]
* A certain ''very'' NSFW site URL begins with ex- (no triple x though) and directly cites the above Futurama quote. [[SchmuckBait It's hit #45389 from 82600 if you ''have'' to google.]]
* This trope is {{discussed|Trope}} during LetsPlay/TheRunawayGuys' LetsPlay of ''VideoGame/MarioParty 4'':
-->'''{{LetsPlay/Chuggaaconroy}}''': Creator/MichaelBay wants to sound like even more of a badass guy so he's like "I am Michael Bay... X!"
* The Website/YouTube 10 year MilestoneCelebration video is an "A-to-Z". The word "experiments" is used for the X.

[[folder:Western Animation X]]
* Protoform X in ''WesternAnimation/BeastWars''.
** Along with Cheetor's line that the pod was branded with "a big, bad-lookin' X!"
* Planet X in the Duck Dodgers cartoons.
** Parodied in one such cartoon: they find Planet X by first searching for Planet A, followed by Planet B, followed by...
* ''WesternAnimation/ThePowerpuffGirls'' were brought to life ''and'' given their ultra-super powers via Chemical X. In one episode Mojo Jojo removes their powers using Antidote X.
* ''WesternAnimation/TeenTitans'' features a villain named Red X. Although he does utilise a variety of tools with an "X" motif, the design of the tools would entirely depend on the user's taste, so the trope still applies.
* "X Agent" from ''WesternAnimation/SheepInTheBigCity''. The trope was parodied in his first appearance:
-->'''General Specific:''' I don't want an "X Agent"! I want a ''current'' agent!\\
'''Private Public:''' The "X" is put in to indicate mysteriousness rather than his job status sir.\\
'''General Specific:''' Well why can't he choose another letter? Like "K"?\\
'''Private Public:''' "K" isn't as mysterious a letter as "X", sir.\\
'''General Specific:''' What about "L"? "L" is pretty mysterious! ''[waving fingers]'' Llllllllllllll...Lllllllll!!!\\
'''Narrator:''' [[LemonyNarrator So, as General Specific re-acquaints himself with the alphabet...]]
* ''WesternAnimation/JohnnyTest'' has Johnny X.
* Dimension X from ''WesternAnimation/TeenageMutantNinjaTurtles1987'', which is alternately described as a distant spiral galaxy or an alternate dimension.


[[folder:Computers X]]
* The operating system UNIX. Originally it was Unics, a pun on "Multics".
** The X Window System for UNIX and Linux (which includes x-terminal, x-clock, etc). Justified--it's predecessor was "W", as in ''windowing''.
* Microsoft seems to like this trope.
** Back in the '80's, they made a version of Unix[[note]] A bit ironic since Windows is now pretty much the only commonly used OS that isn't Unix-derived, but that's beside the point[[/note]] which they called Xenix.
** Windows XP. The XP stands for e''XP''erience, possibly because someone at Microsoft Central had been playing ''TabletopGame/DungeonsAndDragons''.
** Microsoft's "[=DirectX=]" and "[=ActiveX=]" [=APIs=]. What does the X convey about the product, exactly? [[labelnote:actual answer]] The X is short for "Extensions". The Win32 GDI (the standard set of libraries used by Windows programs to perform graphics and input functionalities) proved too bulky and too slow to be used for games, having been designed instead to be a more general set of functionalities for application development. "Direct Extensions," or [=DirectX=], was a library meant to simplify access to low level input/output hardware for graphics, input, sound, and networking. X for eXtension also applies to Intel's MMX instruction set. The other letters varied in meaning, or lack thereof, according to which side of the legal battlefield you were standing on. The X in this case is also the variable 'X', since [=DirectX=] is a collection of several different technologies, such as [=DirectSound=], [=Direct3D=], [=DirectDraw=], etc., though most of those besides Direct3D have been deprecated so when people talk about DirectX nowadays they're usually referring to Direct3D.[[/labelnote]]
** The UsefulNotes/{{Xbox}} falls under this trope as well. Microsoft realized that "[=DirectX=] Box" just didn't sound all that catchy. The Xbox is, essentially, just a computer with streamlined [=DirectX=] support, one of the reasons why it and its successor are touted as being "developer friendly."
* XML (eXtensible Markup Language) and related standards, such as XHTML, XSL (including XSLT and XSL-FO), [=XForms, XPath, XQuery=], [[OverlyLongGag XLink, XPointer, and so on]].
** On a side note, there's actually an older, unrelated [=XForms=](a GUI toolkit), which is completely [[JustifiedTrope justified]] since it was ported from [=IrisGL to X11=].
* Of course, hardware names can't be avoided either:
** The [=XT, ATX, BTX, and DTX=] motherboard design standards. The X supposedly means X-Tended.
** The PCI slot had an upgraded cousin, the PCI-X slot (again, meaning X-Tended).
*** When PCI-Express came about, people thought PCI-X meant that. PCI-Express's unofficial bbreviation is [=PCIe=].
** ATI/AMD and NVIDIA all have an X card.
*** For NVIDIA, up until 2014 the X moniker meant it was a high end card, usually marketed to gamers: the entry level card was the Geforce GT 210, the mid-range card was the GTS 250, and the high end card was the GTX 280; this began to get pushed aside with the Geforce 900 series, which only uses the GT moniker for the lowest end card (like the GT 1030) and starts using the GTX moniker for anything even remotely mid-end like the GTX 1050 all the way to the GTX 1080 Ti. (However, they didn't replace the leading 9 with a leading Roman X -- this is because they would otherwise not have the chance of selling a Geforce GTX Full HD 1080p card).
*** ATI/AMD did this in 2005 when they jumped from the ATI Radeon 9000 series to the X300-X600 series, again in 2016 when they jumped from the AMD Radeon R7/9-300 series to the RX 400 series, then throughout 2017 with the RX 500 and RX Vega series, ''and'' their post-R5/7/9/X cards often get a slightly cheaper trim level with an X at the end of the model, e.g. the [[http://www.eurogamer.net/articles/digitalfoundry-2014-r7-260x-vs-next-gen-console Radeon R7 260X]].
** AMD's CPU division also uses the X moniker. Their old lineup of high performance processors was the FX series, the upcoming Ryzen series will have an X that means they're overclock-ready unlike Intel's K (the AMD Ryzen R7 1800X will be overclockable, like the Intel Core i7 7700K), their chipsets also have an X at the end for the high end models.
** The graphics card company XFX, which also slaps on XXX when one X isn't enough for their souped up graphics cards. So you end up with cards like the "XFX [=GeForce=] 9800 GTX XXX edition."
** Intel uses XE for the "Extreme Edition" processors (it was formerly EE) and, with their part numbers sporting an X. Any high-end chipset also sports an X.
** Intel also has the Xeon line of processors.
** Corsair has its XMS brand of memory.
** The codenames for the Xbox 360's processor and GPU are the Xenon and Xenos, respectively. The UsefulNotes/PlayStation3's GPU is the RSX.
** Creative Lab's X-Fi, for eXtreme Fidelity!
* And some actual computer models:
** Dell's eXtreme Performance System, or XPS. EPS wouldn't be a great marketing name, would it? They also pretty much tacked it on to every computer they have
** Gateway's high end laptops: FX.
** Alienware has the M1#X and the ALX series of computers.
* [[http://en.wikipedia.org/wiki/Pixel Pixel]], which stands for '''pic'''ture '''el'''ements. Which one is kooler[[note]]and easier to spell[[/note]] : 1280x768 picel, or 1280x768 pi'''x'''el?
** Works also as contraction of Pics Elements, Picsel - Pixel.
* ESX stands for Elastic Sky, apparently. (VMware server virtualization product.) X might have stood for the Greek letter chi.
* Products that for some reason go from version "9" into version "X". Roman numerals + XtremeKoolLetterz = RuleOfCool.
** Mac OS X. All previous versions were numbered using Arabic numbers.
*** Apple's DepartmentOfRedundancyDepartment repeats the ten in the version number, so Snow Leopard is Mac OS X 10.6. Apple [[http://support.apple.com/kb/TA22541?viewlocale=en_US insists that the X is pronounced "ten,"]] but usually inserts the word "version" between the two tens (eg. Mac OS X ''v'''10.6). The page just linked is an ironic exception.[[note]]As of version 10.11 (Sierra), the operating system is now known as macOS, for consistency with Apple's other systems (iOS, watchOS, tvOS). Up until this point, the operating system had been known simply as OS X.[[/note]]
** The new version of [=QuickTime=] included with OS X Snow Leopard is so Xtreme that it skipped from version 7 to version X.
** Paint Shop Pro, made by Jasc and then bought by Corel, originally used 1-8 for its version numbers. When Corel bought it, it went from 8 to IX. Then came X, then XI. As the switch happened with 9, not 10, one might be inclined to think this ''might'' not be a case of XtremeKoolLetterz... until the 12th version came out as "X2".
** Partly from superstition about the number 13, and partly so they could have cool letter in its name, the thirteenth version of Wordperfect Office is called X3. (And who is this WP Office owned by? Do we see a pattern here?)
** Adobe in early 2011, released their tenth version of their PDF reader. They also invoked this trope by calling it Adobe Reader X.
*** Adobe then went on to release version eleven as Adobe Reader XI.
* The [=X.500=] cryptography standards. Supposedly this is shorthand for Public Key Infrastructure, which is shortened to PKIX.
* Starting in 2016, {{Sony}} replaced its Xperia Z-series of phones with the Xperia X-series.

[[folder:Others X]]
* Various car manufacturers attach an X somewhere in their car names.
** The hatchback versions of the Honda Civic have an X attached at the end. DX and RX are their most common models.
** Up until 2014, the Toyota Corolla's sporty trim was called XRS and its logo was a huge X with a small RS. After 2014, it's simply a big red S.
** Mazda's line of sports cars sport an X such as the Miata (MX-5) and the RX-7 and RX-8.
** Ford has an XLT version of its F-150 line of trucks.
*** And for years Ford had a compact car called a "[=ZX_"=], peaking in 2005-06 when ''every'' USDM Focus model had such a designation ([=ZX3=]-3 door hatchback, [=ZX5=]-5 door hatchback, [=ZX4=]-sedan, ZXW-wagon).
** Acura's compact hot-hatch is the RSX. Its three SUV models are the MDX, the RDX, and the ZDX. Its new entry level sedan is the ILX. And of course its sports car is the NSX.
*** The NSX is also a case of LetXBeTheUnknown.
** Nissan's Fairlady Z 300ZX, and 180SX/240SX (depends on where do you live).
** Subaru SVX, XV, XT, RX and of course the Impreza WRX.
** Citroën used this trope a lot between [[TheSeventies the 70s]] and {{turn of the millennium}}. Nearly every one of their passenger cars had the letter X in their names. Honourable mention goes to the Citroën ZX.
*** Their trim levels in [[TheNineties the 90s]] were called X, SX, VSX and Exclusive.
*** And as if that [[ExaggeratedTrope wasn't enough]], many of these cars were fitted with an XU-series engine.
** Vespa mostly uses this straight, but inverts it in the LX series; The series was launched in 60th anniversary of the (Italian) company, and LX is Roman numerals for 60.
* Julius Caesar's most trusted elite unit was the 10th legion, which in Latin had the full name ''Legio X Equestris''. His successor Augustus later created the ''Legio X Fretensis'' after Caesar's famous legion, making this trope OlderThanFeudalism. Both legions happened to become famous in history. The Equestris was one of the most important units in the conquest of Gaul. In the Year of Four Emperors, the commander of the Fretensis, which happened to fight a massive uprising in Judaea at the time, split his forces and put an end to the power struggle in Rome and became Emperor Vespasian, while at the same time his son Titus continued to fight the Jewish rebels. Titus led the still famous Siege of Masada and became the first son of an Emperor who succeeded his father to the throne. Later the legion was part of the army led by Trajan against the Persians, who also happened to become emperor.
** Italian fascist government followed the Roman example by naming its elite naval commando unit X MAS (or 10th assault flotilla). They performed a number of daring missions against the Royal Navy in the Mediterranean, especially using saboteur divers (including the mining of battleships Valiant and Queen Elizabeth, which left the British Mediterranean Fleet without a battleship for about a full year).
* The U.S. military enjoys putting X in front of every eXperimental weapon name, along with the usual M. The [=XM16E, XM29, XM25, and XM8 are some recent examples (well not the XM16E)=].
** All the experimental aircraft from the [[http://en.wikipedia.org/wiki/Bell_X-1 Bell X-1]] (first supersonic aircraft) to the [[http://en.wikipedia.org/wiki/Grumman_X-29 Grumman X-29]] (forward-swept wings) -- assuming they didn't skip numbers or that there aren't any others. Also, the [[http://en.wikipedia.org/wiki/XB-70_Valkyrie XB-70 "Valkyrie" bomber]] as well as others.
* Out of all the letters in the alphabet to choose for the default variable in anything, why does "x" have to be it?
** [[http://www.livescience.com/15004-represents-unknown-quantity-variable.html (an unknown) thing -> šay' (arabic) -> xei (Spanish) -> x (abbreviated).]] [[TVTropesWillEnhanceYourLife Now you know.]]
* X-rays: Because "Röentgen rays" just doesn't have the right sound to it. (Reportedly, [[HerrDoktor Prof. Wilhelm Röntgen]] actually preferred the term "X" over his own name, despite the fact that he was was the one that discovered them.)
* Tokyo X, a breed of pig that is known for its quality meat...or a Japanese rock band.)
* The [[http://www.youtube.com/watch?v=Ybp_TcKA5c0 EX-F1]], an amateur-made rail gun.
* The short lived XFL, a particularly good example in that unlike some of the others, the X didn't stand for eXtreme--it was just an X.
* Malcolm Little, who became Malcolm X based on the practice of Nation of Islam converts rejecting their "slave names" and replacing their surnames with X until they earned a new name through a pilgrimage.
* David X. Cohen, a writer for ''WesternAnimation/{{Futurama}}''. When he joined the Writer's Guild, he found his birth name, David S. Cohen, had already been taken, and the Guild has a strict [[OneSteveLimit "No Duplicate Names"]] rule for various legal reasons, so he chose the middle initial X because it sounded sci-fi. If asked what X stands for, he'll often say it just stands for X.
* Many people named Francis X., including the original Francis X. himself, St. Francis Xavier.
* Planet X, the name of a hypothetical planet in the far outer solar system. Not only sounded cool, but had the "X the unknown" thing and would also have been the 10th planet, this being before the discovery of the Kuiper belt and that business with Pluto.[[note]]Actually, it's a bit more complicated than that. "Planet X" was meant to mean "unknown" initially, but would have been the ninth, rather than tenth, planet. When Pluto was found, they thought it was Planet X for years so the term basically disappeared. Then in 1978, they learned just how tiny Pluto was and realised that it couldn't have been Planet X. So Planet X came back, and was now the tenth planet. For about 15 years. In 1992, thanks to the Voyager 2 flyby, they learned that Neptune was a little lighter than initially thought, and so redid their calculations and realised they didn't need Planet X after all.[[/note]]
* Dubai Airport is written as DXB in all shortened forms such as on plane tickets and on arrivals timings.
** LAX, i.e. Los Angeles?
** Also PDX, i.e. Portland, Oregon.
* Practically any time a word starting with "ex-" is shortened for an acronym, the letter X is used, instead of E. This has been particularly true for the word "extreme", which is so often shortened to "X-treme" that many usages don't need to explain themselves, such as the the X Games.
* "Christmas" is often abbreviated as "Xmas" in writing, as the Greek letter Chi, which looks like X, is the first letter of Xristos (Χρἰστος), Greek for "Christ". The "Chi-Rho", which looks like an "XP" in the Latin alphabet and usually written one on top of the other, was an ancient symbol for Christ- "chi rho" ("ch" "r") being the two first Greek letters of the word "Christ".
** And also, X for "Cross", such as [[http://en.wiktionary.org/wiki/ped_xing ped]] [[http://www.colbertnation.com/the-colbert-report-videos/390199/june-21-2011/generic-republican-presidential-nominee xing]].
* Exxon. It doesn't mean anything, it doesn't stand for anything[[note]]though it was a corruption of a prior name ''Esso'', which came from the letters S.O., for Standard Oil[[/note]], it was chosen because it was a) distinctive, b) not already trademarked, and c) sounded cool.
* JAXA: the Japan Aerospace eXploration Agency. Sounds a lot better than JAEA, doesn't it? And it doesn't hurt that it rhymes with NASA.
* On the stock market front, the Toronto Stock Exchange recently changed its initials from TSE to TSX for this simple reason.
* A giant, 40-foot ''Pliosaurus'' found in Svalbard was nicknamed "Predator X" until its formal description was released.
* A Norwegian 6-year old forced his parents to deliver a letter he wrote to the King of Norway, asking for permission to change his name to Sonic X.
* The name Robert X. Cringely, well-known in tech circles, was entirely made up by ''[=InfoWorld=]'' magazine to provide some continuity for one of their columns, which would otherwise have been attributed to a string of short-lived writers. However, one Mark Stephens picked up the column and gained much fame with the Cringely name in the '90s. ''[=InfoWorld=]'' fired Stephens in 1995 and still has other writers filling in as "Cringely," but let him use the name outside of competing magazines as a settlement.
* Brazilian entrepreneur Eike Batista names all of his companies '**X' (EBX, MMX, OGX, MPX, LLX...), because he wants to "multiply wealth".
* Axe Body Spray. They wanted a different name for its UK distribution, so they went with "Lynx," presumably by the time-honored method of "Are there any other short, manly-sounding words with X in them?"
* Sometimes, expressway name abbreviations are written in this way. One example is in UsefulNotes/{{Baltimore}}, where Interstate 83 terminates as the "Jones Falls Expressway" (JFX).
* [[http://www.arxiv.org ArXiv]], the preprint server. (Formerly xxx.lanl.gov, [[https://en.wikipedia.org/wiki/Talk%3AArXiv#XXX a joke to get the site blocked.]] After the total success the joke became a bit counterproductive.)
* Six Flags Magic Mountain has a 4th Dimension roller coaster, formerly known as X.
* Amazons speech assistent "Alexa" is probably an aversion, as the hard "X" should make it easy to recognize in verbal commands, not cool. (Also an allusion to the library of Alexandria.)
* The abbreviation of [[UsefulNotes/MexicoCity Ciudad de Mexico]] is [=CDMX=].