[[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}}''

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 as 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 processors: Athlon X2, Phenom X3, Phenom X4, etc. (They denote how many cores there are.)
* 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.

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

----
!!Examples:

[[foldercontrol]]

[[folder:Anime and Manga]]
* ''Anime/SpeedRacer'' has Racer X. And [[SpeedRacerTheNextGeneration later named a child "X"]].
* ''Anime/SonicX'', but we all know that Sonic is cool anyway.
* ''[[{{X1999}} X]]'', 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]].
* The ''[[LyricalNanoha Magical Girl Lyrical Nanoha]]'' 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''
* ''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 ''TransformersCybertron''.
* The GirlsLove manga ''HayateXBlade'' (where the X is pronounced "cross".)
* The newest chapters of ''Manga/{{Bleach}}'' deal with an organization called Xcution.
* ''RomeoXJuliet'', where the X is still intended to be pronounced "[[RomeoAndJuliet and]]".
* ''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.
* ''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".
[[/folder]]

[[folder:Comic Books]]
* ''Franchise/{{X-Men}}''. Because ex-men just doesn't sound cool enough.
** But for some reason, ''Ex-Mutants'' was...or maybe not.
** 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]] in order to expose said blood to the air. 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 fire]]. Yeah, ''that'' coulda gone better.)
* {{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. CaptainAmerica is Weapon I. But that's a retcon created recently in the scheme of things.)
* Moira [=MacTaggert's=] prisoner, the mysterious MutantX, 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 (''{{Alphas}}'' is sort of a SpiritualSuccessor.)
* The 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.
[[/folder]]

[[folder:Fan Works]]
* ''Literature/HarryPotter'' 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}}.
[[/folder]]

[[folder:Film]]
* 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?
* ''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.
[[/folder]]

[[folder:Literature]]
* 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 ''Unseen Academicals'', we find that Dr. Hicks, 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."
* 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 MadeleineLEngle's book ''A Wind in the Door'' have the power to unmake elements of creation, a process referred to as Xing.
* [[Literature/TheDangerousDaysOfDanielX Daniel X]]
* In ThePendragonAdventure, the biggest competition in Quillain's existence is the Grand X.
[[/folder]]

[[folder:Live Action TV]]
* 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.
** 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 SuperSentai series.
* ''DisneyXD'', or "eXtremely Digital". That's right, little boys, [[WereStillRelevantDammit Disney is cool now and totally not just for girls]].
* ''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]].
[[/folder]]

[[folder:Music]]
* 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 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)"
* The band The xx
* HardcorePunk and [[{{Metalcore}} Metallic Hardcore]] bands (particularly those of the 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.
[[/folder]]

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

[[folder:Professional Wrestling]]
* The seventeenth and eighteenth {{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, {{MTV}}-backed promotion Wrestling Society X.
* 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 VinceRusso's early TNA stable "Sports Entertainment [[XtremeKoolLetterz Xtreme]]"[[note]]Which obviously stands for [[MostWritersAreMale something rather low-brow[[/note]]
[[/folder]]

[[folder:Radio]]
* ''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]]

[[folder:Video Games]]
* The Xbox line of game consoles is the highest profile example in all of video gaming. Although its ancestor, the 8-bit MSX computer line, invoked this trope all the way back in the 1980s.
* ''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 ''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 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 Brawl'' is titled ''Dairantou! Smash Bros X'' in Japan. ''Melee'' was also ''DX'', short for [=DeluXe=].
* Thanks to the 4-character limit in ''VideoGame/FinalFantasyI'' on the NES, X-Zone was named XXXX. X-Zone also appears in ''Final Fantasy VI''.
** 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'' and ''XX''.
* ''PaperMario'' has the X-Nauts.
** And the X-Yux (supposedly pronounced "cross-yux"). Or just the Yux in general.
* ''[[VideoGame/PokemonColosseum Pokemon XD]]'', even if it is a MeaningfulName.
** Certainly ''Pokemon '''ED''' ''wouldn't fly around the US.
** There's also ''[[VideoGame/PokemonXandY Pokémon X Version]]'', which comes with ''[[YNot 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.
* Every member of the Organization XIII in the ''Franchise/KingdomHearts'' series have an X in their names in a form of ThemeNaming -- their names are an anagram of their original name, 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"
** 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 it's wielder can fire a SwordBeam, of course in the shape of an X.
* The Japan-only GameBoy game ''X'' and its [=DSiWare=] sequel [[http://www.youtube.com/watch?v=7lfPZ75XcpQ X-Scape]]
* The DSiWare game ''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 ''[[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 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 [[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.
* Sega's 32X system.
* The early online adapter for the Genesis and the SNES, the 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 Playstation was PS-X, short for PlayStation-eXperimental. Later, Sony released a digital video recorder with integrated Playstation and Playstation 2 hardware, called PSX.
* The PSX...err, ''PS1'' games ''1Xtreme'', ''2Xtreme'', and ''3Xtreme''. Supposedly they are a combination of racing and eXtreme sports, as in rollerblades and skateboards.
* [[VideoGame/GrandTheftAutoIV Playboy X]]
* ''VideoGame/{{X-Com}}''. 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"]]).
[[/folder]]

[[folder:WebOriginal]]
* 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 ''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!"\\
[[/folder]]

[[folder:Western Animation]]
* 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.
* The ''PowerpuffGirls'' 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]]

[[folder:Webcomics]]
* ''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, it's 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/{{X-Men}} his team of sorcerers]], and thought the name "Xavion" sounded cool.
[[/folder]]

[[folder:Computers]]
* 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''.
* Windows XP. The XP stands for e''XP''erience, possibly because someone at Microsoft Central had been playing ''TabletopGame/DungeonsAndDragons''.
* 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 eXtended.
** The PCI slot had an upgraded cousin, the PCI-X slot (again, meaning eXtended).
*** 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, even though ATI/AMD stopped this moniker a while ago. For NVIDIA, the X moniker means it's the high end card, usually marketed to gamers.
** 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.
** AMD is guilty of the X moniker. Their old lineup of high performance processors was the FX series. Their chipsets also have an X at the end for the high end models.
** Corsair has its XMS brand of memory.
** The codenames for the Xbox 360's processor and GPU are the Xenon and Xenos, respectively. The [=PlayStation=] 3'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
** IBM PC-XT.
** 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?
* ESX stands for Elastic Sky, apparently. (VMware server virtualization product.)
* Products that for some reason go from version "9" into version "X". Roman numerals + XtremeKoolLetterz = RuleOfCool.
** Mac OS X. All previous Mac OS's 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.
** The new version of [=QuickTime=] included with OS X Snow Leopard is so Xtreme that it skipped from version 7 to version X.
** The [=ATi=] X series of video chipsets, which came after the 9000 series.
** 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.
* 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.[[/labelnote]]
** The {{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."
* The [=X.500=] cryptography standards. Supposedly this is shorthand for Public Key Infrastructure, which is shortened to PKIX.
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[[folder:Others]]
* 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.
** 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 was the NSX. A new NSX model is coming around 2015.
*** The NSX is also a case of LetXBeTheUnknown.
** Nissan and its 180SX/240SX (depending on where you live)
** Subaru Impreza WRX
** 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.
* The X games, even if X is supposed to be for eXtreme.
* Out of all the letters in the alphabet to choose for the default variable in anything, why does "x" have to be it?
* X-rays. "Roentgen rays" just doesn't have the right sound to it.
** In Germany, they're actually called like that: Röntgenstrahlen.
** In Sweden, they're called Röntgenstrĺlar.
*** They're called "Röntgen rays" in roughly half the languages in the world (and "X-rays" in the rest, of course), so it's not the most valid example out there.
** Reportedly, [[HerrDoktor Prof. Wilhelm Röntgen]], the very discoverer of such rays, actually preferred the term "X" over his own name for the then newly found type of radiation.
* 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.
* 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 an 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.
* Dubai Airport is written as DXB in all shortened forms such as on plane tickets and on arrivals timings.
** LAX, i.e. Los Angeles?
* Practically any time a word starting with "ex-" is shortened for an acronym, the letter X is used, instead of E.
* "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".
** 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.
* 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.
* 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).
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