Short for "'''killer application'''", a '''killer app''' is a game - or something not a game that's a category killer - so good that it's considered a must-own if you have the system it's released for, and is in fact a reason in and of itself to buy said system.

When you buy {{literature}}, you get a single self-contained experience: the book contains all there is to this particular adventure. When you buy a ticket for a {{film}} or a [[{{Theatre}} stage show]], you get two hours of drama, and that's all there is to see (until the inevitable sequel, that is). But electronic hardware isn't like that. Music players, movie players, computers, video game consoles, tablet computers... They all require ''software'' to run, and each piece of software delivers a different experience: a photo-editing suite can't be used to balance your checkbook, for instance, or vice versa. As such, hardware and software are separate but interlinked categories, and one is used to judge the other: the same piece of software might run much more efficiently on one computer than another, and you'd factor that in when deciding what hardware ''or'' software to buy. And, just to add to the confusion, a fair amount of software is ''exclusive to one piece of hardware'', or family of hardware: for instance, Microsoft for the longest time resisted releasing its "Office" suite of productivity software (Word, Excel, [=PowerPoint=], etc) for [=iPad=], to keep their competing "Surface" tablets relevant.

And that's where we get to this trope. A "killer app" is a piece of software that validates the hardware. It provides such an excellent user experience that it justifies buying the hardware.

The term is primarily used within the world of video gaming, but originated outside it: it was used, especially during the '90s Internet boom, to describe the mythical invention that everyone in America needed and which would make its developers -- and their investors -- rich beyond their wildest dreams. The term can also be used on a more serious context, used to refer to a very useful application which immediately becomes a "must-have". When the term is applied in this manner, only a very few applications apply, including word processors, spreadsheets, database management programs, email clients, and web browsers. The only thing everyone agrees on is that any new hardware attempting to launch itself should have a Killer App at hand, especially if the hardware itself is a video game console--that business is more software-driven than any other.

While most products that attain killer app status are extremely successful and popular, it should be noted here that "creating a true killer app" is akin to "writing the Great American Novel": everybody ''wants'' to, but nobody has yet created (or is likely to create) the definitive killer app.

Note that a killer app is more than just a good game. A game can be good, great, critically acclaimed, even an all-time classic... and still not be a killer app (conversely, not all killer apps are great by modern standards; some of them seem quite dated today). A killer app is insanely popular in its own time, enough so as to single-handedly drive sales for its system. The examples that follow, then, are not just the games that tropers loved, but rather the games that ''everyone'' loved; the ones that made their respective systems.

Arguing over which killer app provides the most bang for its buck is a large part of the ConsoleWars.

Compare StarMakingRole (equivalent for actors) and BreakthroughHit (equivalent for creators).

%% And don't list killer apps that "might be". Wait until the results, even if they get listed as "failed to be one".

* ''VideoGame/SpaceInvaders'' was a major system mover for the UsefulNotes/{{Atari 2600}}, quadrupling its sales, making it the UrExample.\\\
Atari was counting on both ''VideoGame/PacMan'' and ''Film/ETTheExtraTerrestrial'' to be killer apps for the 2600, and had each produced in wildly optimistic numbers; in fact, more ''Pac-Man'' cartridges were produced than there were Atari consoles, on the assumption that the game would be so popular people would buy consoles just to play it. As it turned out, they were only half-right, as [[IncrediblyLamePun they did help to kill the Atari 2600]], [[TheGreatVideoGameCrashOf1983 and very nearly the entire industry]].
* ''VideoGame/StarRaiders'' was a bona fide KillerApp for the UsefulNotes/Atari8BitComputers; many people bought the computer just to play the game.
* ''AlienVsPredator'' and ''{{Tempest}} 2000'' were this for the otherwise ill-fated [[UsefulNotes/AtariJaguar Jaguar]].
* On the computer side of Atari, the presence of MIDI ports was what made the UsefulNotes/AtariST the go-to machine for electronic musicians.

* Coleco's competitive acquisition of the console license for Creator/{{Nintendo}}'s ''VideoGame/DonkeyKong'' is the main reason the UsefulNotes/ColecoVision console was a contender in the second generation ConsoleWars. It is rumored that the company released an intentionally poorly-designed version of the game for the Atari 2600, just to make their own system look even better by comparison.

* The first ''VideoGame/SuperMarioBros'' for the original UsefulNotes/{{N|intendoEntertainmentSystem}}ES, credited with saving a dying video game industry. ''VideoGame/SuperMarioBros3'' followed a few years later.
* ''VideoGame/SuperMarioWorld'' for the UsefulNotes/{{S|uperNintendoEntertainmentSystem}}NES, which was packaged with all SNES units. ''Super Mario All-Stars'', a updated compilation of the NES Mario games (including the first domestic release of "The Lost Levels" of the original Japanese Mario Brothers 2), also proved the viability of the UpdatedRerelease concept. It's one of the most heavily modded games in history.
* The SNES also floated high on ''VideoGame/TheLegendOfZeldaALinkToThePast'' and the port of ''VideoGame/StreetFighterII'', which was packaged with the console in some countries. The ''VideoGame/DonkeyKongCountry'' series also allowed the SNES to remain popular into the 32-bit era, while Sega stumbled with the [[OtherSegaSystems Sega CD, 32X]] and SegaSaturn confusion.
* The UsefulNotes/VirtualBoy didn't really have much going for it, but those who have played ''VideoGame/VirtualBoyWarioLand'' agree that it was the one game truly worth playing on the console.
* Initially ''VideoGame/SuperMario64'' and then ''VideoGame/MarioKart64'', ''VideoGame/GoldenEye1997'', ''VideoGame/TheLegendOfZeldaOcarinaOfTime'', ''VideoGame/TheLegendOfZeldaMajorasMask'', ''VideoGame/{{Banjo-Kazooie}}'' and ''Banjo-Tooie'', ''VideoGame/PerfectDark'', ''VideoGame/DonkeyKong64'', and ''VideoGame/StarFox64'' for the {{Nintendo 64}}. The system became famous for releasing two to three Killer Apps a year, and is considered to this very day one of Nintendo's greatest consoles.
* ''VideoGame/SuperSmashBros Melee'' is the absolute [=GameCube=] killer app, its quality '''far''' surpassed its predecessor, and it's still being played [[TournamentPlay competitively]] more than 10 years after its release, a life of a FightingGame surpassed only by ''VideoGame/MarvelVsCapcom2'' by '''1 year'''.
* ''VideoGame/ResidentEvil4'', ''VideoGame/EternalDarkness: Sanity's Requiem'' and ''VideoGame/MetroidPrime'' convinced the hardcore gamers that the GameCube wasn't a kiddie wasteland. The Gamecube even had the most M-rated games out of any Nintendo console. To quote the Top 10 GameCube games video from ScrewAttack:
-->''When [[VideoGame/MetroidPrime this game]] was first announced, [[TaintedByThePreview we thought it was going to]] '''suck'''. How wrong we were. How wrong we were.''
** ''Resident Evil 4'' was even released as part of Capcom's initiative to bring five new exclusive games to the GameCube to support the platform. Unfortunately, one of them (''Dead Phoenix'') was [[{{Vaporware}} never released]], three of them (''Resident Evil 4'', ''VideoGame/ViewtifulJoe'', ''VideoGame/{{Killer7}}'') were eventually ported to the {{PlayStation 2}}, and the only game to remain a GameCube exclusive (''VideoGame/PN03'') didn't sell many copies and was critically panned.
** At the console's release, ''Franchise/StarWars: VideoGame/RogueSquadron 2'' was considered the Gamecube's Killer App at launch and even held the title after Smash Bros Melee was released a couple months later. When the console was released in Europe, Rogue Squadron 2 was it top selling game, beating out Nintendo's first party titles.
* The UsefulNotes/{{Wii}} is an unusual case in that it has had a dozen or so killer apps, but relatively few quality third party titles. At launch, the general public bought it for ''VideoGame/WiiSports''. For hardcore gamers, it was ''VideoGame/TheLegendOfZeldaTwilightPrincess''.
** 2007 saw ''Wii Play'', which helped ensure that most Wii owners would have multiple controllers, party games like ''Mario Party 8'' and ''Mario and Sonic at the Olympic Games'', and ''Super Mario Galaxy'', the 2nd best selling 3D platformer of all time. ''Wii Fit'', which was released in the West in 2008, was more popular than the [=PS3=] for a while, but support for the peripheral hardware never caught on.
** 2008 had ''Mario Kart Wii'' and ''Super Smash Bros. Brawl'' Nintendo's premiere games for multiplayer and the best selling games in the history of their genres. The new ''VideoGame/AnimalCrossing'' and ''Wii Music'' were likely meant to become Killer Apps, but poor reception amongst the hardcore audience turned these into mere hits.
** 2009 was another year of multiple killer apps. ''VideoGame/NewSuperMarioBrosWii'' was the big holiday title, and is often given at least partial credit for the resurrection of platformers on consoles. ''Wii Sports Resort'' popularized the Wii [=MotionPlus=], which would be used in other games such as ''Skyward Sword''.
** Since 2009, Ubisoft's ''Just Dance'' games have also become this for the Wii; one of the only games more popular with girls than with boys. However, the lack of big releases since late 2009 has been tied to the Wii's relative decline compared to the other 7th generation consoles.
* The WiiU has had an extremely slow first year, and part of the problem seems to be that there hasn't been a must-have Killer App for the system yet. While there have been some good titles, the real system-sellers are expected to be ''VideoGame/MarioKart 8'' and ''VideoGame/SuperSmashBros for [=WiiU=]''.
** In April 2014, Nintendo started ''really'' pushing ''Mario Kart 8'' to an almost aggressive extent. In addition to releasing a premium Wii U bundle in many regions [[note]]The North American bundle includes the game, a complete Wii U Deluxe system, a Mario-themed Wii Remote Plus and Wii Wheel; Europe gets a similar bundle plus two special Mario and Luigi-themed bundles that include some additional goodies such as a strategy guide[[/note]] they've also launched a program so that between May 30th (its release date) and July 31st, ''every'' copy that has been purchased--including those that come in the bundle--can be registered on Club Nintendo, their consumer loyalty program. The reward? One ''free Wii U game of your choice'' on top of everything else. North America gets 4 options to choose from[[note]]''VideoGame/NewSuperMarioBros U'', ''Wii Party U'', ''VideoGame/TheLegendOfZeldaTheWindWaker HD'', and ''VideoGame/{{Pikmin}} 3''[[/note]], while Europe and Australia get 10[[note]]The four aforementioned games plus ''VideoGame/TheWonderful101'', ''VideoGame/MonsterHunter 3'', ''VideoGame/SonicLostWorld'', ''[[VideoGame/WarioWare Game and Wario]]'', ''VideoGame/NintendoLand'', and ''[[VideoGame/MarioAndSonicAtTheOlympicGames Mario and Sonic at the Sochi 2014 Olympic Winter Games]]''[[/note]]. As a result, ''Mario Kart 8'' sold 1.2 million copies in its first weekend alone and boosted the console's sales in every region. Wii U sales in Europe, for example, rose by ''666'' percent.
** There's also ''VideoGame/EarthBound'' being released for the Wii U's VirtualConsole, which became one of the top downloaded titles for the service. Not bad for a game that was an AcclaimedFlop when it first came out.
** ''VideoGame/DonkeyKongCountryTropicalFreeze'' additionally sold 130,000 copies (physical and digital) on its first eight days of release in the US alone, causing a 25% increase in hardware sales from one year prior. Not too shabby.
* ''VideoGame/CastlevaniaCircleOfTheMoon'' was considered a Killer App when it was first released for the Game Boy Advance. However, more than anything, the GBA was built on the base of the UpdatedRerelease, with every quality SNES title ported over for a new generation to open their wallets for, along with new nostalgia-heavy franchises like ''VideoGame/WarioWare''. Likewise, ''VideoGame/PokemonRubyAndSapphire'' catalyzed the GBA sales at a very high rate. They ''are Pokémon'' [[CashCowFranchise games]] after all.
* The UsefulNotes/GameBoy[='s=] original killer app was ''VideoGame/{{Tetris}}'', but the aging system was revitalized late in its lifespan by another smash hit: ''VideoGame/PokemonRedAndBlue''. The various sequels of the latter have kept the tradition, driving large sales of their native platforms.
** To put this in better perspective, ''multiple Pokémon'' games are among the best-selling Game Boy Advance and DS games. The best selling titles on the Game Boy Advance were ''Ruby and Sapphire'', which sold over 15 million units, ''[=FireRed/LeafGreen=]'', which sold over 10 million units, and Emerald, with over 6 million units. Even the ''VideoGame/PokemonMysteryDungeonRescueTeam'', a spinoff by a 3rd party which also was sold on the DS as Blue version, was one of the system's top 20 selling titles, beating out games like ''Franchise/KingdomHearts'', ''VideoGame/GoldenSun'', ''VideoGame/MetroidFusion'', and ''VideoGame/TheLegendOfZeldaTheMinishCap''. The series was not quite so dominant on the DS, but this was due to the market's growth outstripping the franchise, not a loss in popularity.
** ''Pokémon'' is currently the second-best selling series in the world, with the Super Mario series (not counting spin-offs) leading by a mere 40 million games sold. After a ''ten year'' headstart. It remains to be seen if it will pass its older brother, it's too close to call at this point.
** ''VideoGame/PokemonBlackAndWhite'', came out in September 2010, and it's already the fastest-selling DS game in history.
** It's more than likely sales of the 3DS surged in anticipation for ''VideoGame/PokemonXAndY'' It ended up selling four ''million'' copies in its first two days of sales and became the fastest-selling 3DS game of all time. (It probably didn't hurt that ''X'' and ''Y'' were the first ''Pokémon'' games to be released globally, rather than separate release dates for each region.)
* ''VideoGame/{{Nintendogs}}'', ''VideoGame/BrainAge'' (for older gamers), ''VideoGame/MarioKart DS'' and ''VideoGame/NewSuperMarioBros'' (for the Nintendo Faithful), ''VideoGame/AnimalCrossing: Wild World'', and its quirkier casual games in general, for the NintendoDS.
** The remake of ''VideoGame/FinalFantasyIII'' wasn't a system killer app as much as a third party support killer app. The same could be said for the remake of ''VideoGame/FinalFantasyIV''.
** ''VideoGame/GrandTheftAutoChinatownWars'' wasn't quite the Killer it was expected to be on the DS, but made a huge impact on [[IOSGames the iPhone platform.]] Its success essentially gave the greenlight for other developers to create DarkerAndEdgier games for your iPhone or iPod Touch.
* ''VideoGame/TheLegendOfZeldaOcarinaOfTime'' [[ again, this time]] for the Nintendo3DS. Within two weeks, it had sold over 600,000 copies, or over 20% of the install base. It raised 3DS sales by over 50% the week it came out, despite not being released in America until the next week.
** ''VideoGame/MonsterHunter 3G'' (at least if you live in Japan).
** Those last two games were the two best selling games in Japan during 2011, despite only being out for less than two months. ''VideoGame/SuperMario3DLand'' sold over five million copies in just two months worldwide, outselling games like ''VideoGame/GearsOfWar 3'' and ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'' on the 360. ''Mario Kart 7'' sold 4.3 million in 5 weeks. Put together, the two Mario games represent a third of 3DS software sold in 2011. Combine those Mario games with ''Ocarina of Time'' and ''{{Nintendogs}} + cats'', you have over one half of all 3DS software sold through 2011.
** ''Animal Crossing: New Leaf'' seems to have become Japan's new killer app for the 3DS. The game sold two million copies in less than six weeks - the first 3DS game to reach that milestone in Japan - and has remained at the top of the Japanese charts since its release in November 2012. In the US, some have called it a Killer App for Nintendo's release of triple-A titles digitally through the E-Shop services, being a game for which having constant access on your systems at any time adds enough to the experience to assuage concerns over the lack of physical ownership of a cartridge.
** ''Super Smash Bros. 4'' for 3ds sold a million copies in its opening weekend in Japan alone. Though only time will tell if it surpasses ''VideoGame/PokemonXAndY'' after its international release.
* DSiWare had ''PhotoDojo'', a fighting game where you could take pictures/sound recordings to create fighters, including yourself. Also, you could make your own stages this way.
* When the NES first launched it came with R.O.B., your [[RobotBuddy Robotic Operating Buddy]]. R.O.B. could play two games, both of them borderline unplayable, and the R.O.B. itself only seemed to function half the time. However, it was key in making the system seem less like a "videogame console" (which was a dirty word at the time, considering the video game crash of the early 80's). Essentially, it was a ''fake'' Killer App... something that seemed like the must-own technology of the future that handily snuck some more important hardware into homes.

* The ''Franchise/SonicTheHedgehog'' series on the Mega Drive[=/=] UsefulNotes/SegaGenesis, as well as the first ''VideoGame/MaddenNFL'' game for (U.S.) sports fans. The bloody version of [[VideoGame/MortalKombat the first]] ''Franchise/MortalKombat'' also was a boon in distinguishing it from the SNES.
* The Genesis port of the arcade version of ''VideoGame/{{Strider}}'' was also one of the system's earlier killer apps. In addition, the game holds the distinction of being the first game to be released on an 8-megabit cartridge.
* The Genesis Version of ''Disney/{{Aladdin}}'', made by Virgin Interactive in partnership with actual Disney animators, was the 3rd best selling game for the system, and this version did not come to the SNES, due to Capcom still holding the rights to make Disney games on Nintendo systems at the time. While the SNES version was a good game too, The Genesis version was more of a labor of love for Disney fans while the SNES version was more generic.
* When ''VideoGame/LunarSilverStarStory'' was released in Japan, it sold almost as many copies as the SegaCD. That, and ''VideoGame/SonicTheHedgehogCD'', were, if not killer apps, the nearest thing the Sega CD/Mega CD had.
* Sega's ''VideoGame/VirtuaFighter'' was such a huge hit in arcades that its various ports sold more than half of all 32X and Saturn machines in Japan.
** ''Virtua Fighter 2'' was the killer app for Saturn.
** ''SakuraTaisen'' was the other Saturn killer app in Japan. It, and the second game recorded the biggest sales as a Saturn original title, and was ranked #13 place in the Famitsu's 100 all-time favorite games list, leading the series to become one of Sega's most successful franchises.
* The ''VideoGame/PanzerDragoon'' series are killer apps for the Saturn, despite the fact that the first was the only one that sold well.
* ''VideoGame/NiGHTSIntoDreams'' served as a primary reason to buy a Sega Saturn. Other games for the system with massive popularity include ''VideoGame/VirtuaFighter'' and ''[[VideoGame/{{Bomberman}} Saturn Bomberman]]'' (often referred to by reviewers as the best game in its series).
* The beyond-the-arcade port of ''VideoGame/SoulCalibur'' was ''the'' reason to get a {{Dreamcast}}, even though it wasn't enough to move sales of the system. Interestingly, the death of the Dreamcast (and the end of Sega's hardware history) was heralded by EA denying Sega a port of ''VideoGame/MaddenNFL'', the same killer app that made their own company what it is today, and wouldn't have done so without the parent company's help. EtTuBrute
** However, ''[=NFL2K=]'' was one of the rare sports killer apps, becoming one of the biggest sellers at launch along with ''another'' killer app in ''VideoGame/SonicAdventure'' (The final true Sonic killer app), and garnering enough rave reviews that it instigated a still-strong backlash against ''Madden NFL'' once EA won the bid to become the sole manufacturer of NFL games. Although Sega was able to fill the void with that and its equally-well-received ''NBA 2K'' counterpart, no EA support did punch a big hole in the DC's third-party support.
** ''VideoGame/{{Shenmue}}'' had generated considerable hype for the console, and is widely considered the best game on it, but its huge budget eventually led to it becoming a financial failure despite solid sales.

* When the TurboGrafx16's CD add-on came out, NEC's marketing division, TTI, was quick to promote the two CD ShootEmUp titles available for it, ''Gate of Thunder'' and ''Lords of Thunder'', as being its flagship titles, even ahead of console mascot Bonk. ''VideoGame/{{Ys}} Books 1 & 2'' was also highly lauded. In Japan, the first big game produced for the CD-ROM unit was ''VideoGame/TengaiMakyou: Ziria'', but neither it nor its more popular sequel was ever exported.

* ''VideoGame/BattleArenaToshinden'' was hyped as the first killer app for PlayStation, a "''VideoGame/VirtuaFighter'' Killer". It took at first, but the quality of later games overtook it and now it's currently forgotten. The real killer apps ended up being ''VideoGame/ResidentEvil'', ''Franchise/TombRaider'', ''VideoGame/MetalGearSolid'', and especially ''VideoGame/FinalFantasyVII''. And to a lesser extent, the ''Franchise/CrashBandicoot'' and ''Franchise/SpyroTheDragon'' series. The system's sheer number of killer apps is the main reason it was able to take the video game throne from Nintendo in the mid '90s.
** {{Squaresoft}}'s decision to develop ''VideoGame/FinalFantasyVII'' for the PlayStation over the N64 played a huge role in Sony's victory over Nintendo during the 32/64-bit era.
* The {{PlayStation 2}} received four major killer apps in 2001: ''[[{{GranTurismo}} Gran Turismo 3: A-Spec]]'', ''VideoGame/FinalFantasyX'', especially ''VideoGame/MetalGearSolid2SonsOfLiberty'', and ''VideoGame/GrandTheftAutoIII''. Coincidentally -- or perhaps not -- this coincided with release of two of its competitors' consoles, GameCube and Xbox.
** Due to the anticipation generated by its pre-release hype, ''VideoGame/MetalGearSolid2SonsOfLiberty'' is credited for the PlayStation 2's victory over the Dreamcast before the game was even released. The game then went on to being one of the top 10 best-sellers, with over 7 million copies sold.
** The ''VideoGame/GrandTheftAuto'' series of games had been killer apps for the PlayStation from ''GTAIII'' onwards[[note]]Rockstar did release Xbox and PC versions, but they came later[[/note]] until Microsoft pulled a major coup and convinced Rockstar to make ''VideoGame/GrandTheftAutoIV'' a multi-platform release on day one.
** ''VideoGame/MetalGearSolid3SnakeEater'' is widely considered one of the PS2's best games (if not the best), and also one of the system's top 10 to top 15 best-sellers.
** Also of note is the ''Franchise/RatchetAndClank'' series, which was so successful, Ratchet ended up becoming the new face of Sony after Crash and Spyro went third-party.
** The PS2 had so many killer apps lined up that ''VideoGame/GodOfWar'' doesn't make this list simply because it just flat-out wasn't needed.
* The ''VideoGame/GranTurismo'' series were killer apps on the [=PS1=] and [=PS2=], but Sony Computer Entertainment's fumbling of the [=GT5=] release may have prevented this status for the [=PS3=]. But that's not the case for [=GT6=], which not only received alot of support from car companies(Vision GT is an example), but also got a great reception from the fans for being a huge upgrade from [=GT5=].
* ''VideoGame/MetalGearSolid4GunsOfThePatriots'' was the biggest killer app for the PS3, and what ended most of the hate for the system. What's most notable is that Snake's [[GuestFighter appearance]] in ''VideoGame/SuperSmashBrosBrawl'', specifically his own stage, has a massive amount of {{Foreshadowing}} for this game. ''[[{{Irony}} Foreshadowing on the killer app of a direct competitor]]''.
** ''VideoGame/GodOfWar III'', though not hurt by being released at the time the price cut was taking effect.
** The ''VideoGame/{{Uncharted}}'' series has been this, but it has never been more apparent than with ''Uncharted 3: Drake's Deception'', which sold [[ 3.8 million copies during the first day of release]], something rarely heard of for console exclusive games.
** ''VideoGame/{{Killzone}} 2'', which is essentially the ''Halo 3'' for the [=PS3=].
** ''VideoGame/TheLastOfUs'' [[ has sold 6 million]] in less than a year, making it the 2nd best-selling exclusive behind ''Gran Turismo 5'', and 3rd best-selling PS3 game overall.
* ''VideoGame/{{Persona 4}}: [[UpdatedRerelease The Golden]]'' is this for the Vita in Japan, which was lagging behind. It sold 137 thousand copies along with 34 thousand units. This later proved true for the Western market as well.
* ''VideoGame/GravityRush'' became this for the UsefulNotes/PlayStationVita as it was offered for free for Playstation Plus members for the better part of two years since its launch release.

* The ''Franchise/{{Halo}}'' franchise cemented the Xbox as "the {{FPS}} console", leading to the FPS "arms race" between Microsoft and Sony that lasted through TheNoughties. ''VideoGame/{{Halo 2}}'' is this for the XboxLive multiplayer service, ''VideoGame/{{Halo 3}}'' is this for the {{Xbox 360}}, and ''VideoGame/HaloCombatEvolved'' single-handedly saved Microsoft from being a mere footnote in the Console Wars.
* The game that proved the Xbox could do something ''other'' than FPS was ''Videogame/KnightsOfTheOldRepublic'', which spurred sales off the console close to ''Halo'' levels.
* ''VideoGame/GearsOfWar'' and ''VideoGame/{{BioShock|1}}'' were among the first great games for the Xbox 360.
* Like the GameBoyAdvance, XboxLiveArcade has sold mainly on a stream of solid indie, ranging from ''GeometryWars'' to ''VideoGame/SplosionMan''.
* This trope is mostly inverted when it comes to Japan, as they has not taken to either system much like it's competition. So far, the closest the 360 has to a killer app there is a hit game that boosts sales for a week or so then they fall back to just selling a few thousand a week until the next hit game. These "boost" games include ''BlueDragon'' (AkiraToriyama's involvement helped, too), ''AceCombat6'', ''VideoGame/TalesOfVesperia'' (which is the best-selling 360 game in Japan and was even sold with [=360s=] for a while, so it was a {{Fanboy}} issue when it was later ported to the [=PS3=]) and ''VideoGame/StarOceanTheLastHope''.
** For [=XboxLive=] in Japan, the Killer App is ''VideoGame/TheIdolmaster'', even if it isn't for the 360 itself. On the release of the Xbox 360 version, Microsoft sold over 4 times as many Microsoft points as they had in the past. THE iDOLM@STER singlehandedly resparked the sales for the [=XBOX 360=] on Japan. The success was so great that in some stores they had to close the doors at early in the morning because they were sold out.
* The ''Videogame/ForzaMotorsport'' series is Microsoft's racing killer app, designed to target the Playstation's ''Videogame/GranTurismo'' series. ''Forza'' has sold millions, and the [[LoadsAndLoadsOfCharacters wide variety of cars]], [[DesignItYourselfEquipment customization]], and [[{{Itasha}} painting]] makes it '''the''' go-to racing simulator for the Xbox.

* The original classic Mac's killer app was its four channel sampled audio, a feature very nearly nixed by Steve Jobs. The feature went on to become the Mac's selling point in the US as the feature meant that the Mac could have "talkie" games that were impossible with [=PCs=] of that era. ([=PCs=] only started having sound cards that was capable of sampled audio with the Sound Blaster , which was released in 1989. The Mac had sampled audio support since its birth in 1984). The demonstration of [=MacinTalk=] during it's launch was one of the major selling points. This, combined with the fact that early '90s Macs were the also the first computers to ship with CD-ROM drives as standard equipment, cemented its status as an edutainment machine in schools and as the all-rounded family multimedia machine in homes in the '90s. Of course, it helped that VideoGame/{{Myst}} was one of the killer apps for the platform, appearing for the Mac first before being ported to Windows [[note]]Myst was originally written in [=HyperCard=], a Mac-specific programming language[[/note]].
* '''''Videogame/{{Doom}}.''''' The biggest Killer App in all of PC gaming history, with over 4 million copies sold. Before ''Doom'', PC games were a niche hobby, a small subset that was to console[[note]]or, to put it in more periodic terms, "Atari/Nintendo/Sega"[[/note]] players what video games were to the general populace. ''Doom'' made PC gaming mainstream, and let the world know that those computers they were using for their essays and spread sheets could do something that not just matched, but even ''surpassed'' what those boxes next to their [=TVs=] could do. To call it the ''Franchise/SuperMarioBros'' of PC gaming is an understatement; it singlehandedly ''made the PC the new Nintendo'', and only after its success can you watch a movie or TV show and see anybody playing video games on their computers as opposed to sitting by the television playing on a console. Even to ''this very day'' it's the first (and often only) title that comes to non-gamers' minds when they think of PC games, with ''VideoGame/CallOfDuty'' only recently supplanting this honor.
** ''Doom'' was indirectly the TropeMaker for Windows as a serious gaming platform. Prior to Windows 95, you were limited to ''Solitaire'' and ''Minesweeper'' and the occasional more advanced title like ''Myst''. And then Bill Gates read the result of a study that found that ''Doom'' was installed on more computers in the world than Windows was. Intent on remedying this, Bill made damn sure that Windows 95 would have its own compatible version of ''Doom''.
* The most important game on PC in terms of actually ''selling hardware'' was ''Links 486''. This game actually forced owners to upgrade from 386 to 486 processors '''''just to play it'''''.
* Try thinking of a PC game before ''VideoGame/KingsQuest''. Outside of the ''VideoGame/{{Zork}}'' series of {{Text Adventure}}s, it's not a very easy task. The colorful, imaginative adventures that Creator/{{Sierra}} brought to life gave gamers something appealing that console games, with their straightforward running and jumping and shooting, just couldn't offer: an interactive, immersive world you could get lost in as it unfolded in vivid graphics, text details and cutscenes. [[SeinfeldIsUnfunny Even if they aren't exactly vivid by today's (or even the latter half of the decade's) standards]], it was enough to convince a lot of people why you would want to play video games on the "homework machine".
* {{Creator/Bungie}} seems to make killer apps wherever they go. [[AppleMacintosh Mac's]] killer app? The ''VideoGame/{{Marathon}}'' Trilogy. The Xbox's? ''{{Franchise/Halo}}''.
* In the same vein as ''Doom'', ''VideoGame/HalfLife'' and its sequels pushed the success of PC games even further, with their slick design and fantastic presentation bridging the gap between "casual" gamers raised on mascot platformers and Japanese [=RPGs=] and "hardcore" gaming formats.
** ''VideoGame/CounterStrike'' was, ironically, both the killer app for the early 2000's golden age of 'real world' LAN Gaming cafes/centres, as well as the reason they crashed in popularity from 2004 onwards, when the Source remake became the killer app for {{Steam}} and home-based online multiplayer.
** Valve did it again with ''VideoGame/TeamFortress2'' in 2007, which is, to this very day, their most successful game ''of all time'', and tied with ''VideoGame/{{DOTA 2}}'' (also by Valve) as the most popular game on Steam.
* ''StarWarsRebelAssault'' was THE killer app for CD-ROM, although some say that the time of CD-ROM had dawned and ''Rebel Assault'' was just the first major game...
* There are two candidates for the cross-platform killer app for CD-ROM drives: ''VideoGame/TheSeventhGuest'' and ''VideoGame/{{Myst}}'', both often bundled with the drives people bought in order to play them. Interestingly, unlike many of the other games on the list, they currently have a bit of a SeinfeldIsUnfunny status.
* Attempts had been made for ages to sell 3D accelerators, and while 3dfx's Voodoo made a good argument, it was ''VideoGame/{{Unreal}}'' that caused people to pour hundreds of dollars into enough system upgrades to see it rendered through Glide.
** You mean ''[=GL=]VideoGame/{{Quake}}'' wasn't reason enough? (While it's not the first 3D-accelerated version of ''Quake'', with ''[=VQuake=]'' for Rendition Verite cards having been released earlier, ''[=GLQuake=]'' made 3dfx Voodoo Graphics cards sell like hotcakes.)
* ''VideoGame/{{Crysis}}'' has been a boon to graphics card manufacturers, as hardcore computer gamers have been working hard to build systems that can render its incredible graphics at full detail, even ''four years'' after its release!
** It was also important because at the time, other developers who weren't abandoning the PC altogether were [[PortingDisaster making ports that used graphics vastly inferior]] to that of an {{Xbox 360}} or a PlayStation3 for no good reason and the rest of the time just ported in the laziest way possible, leaving the inferior graphics and control schemes of the consoles. Some say that this game single-handedly saved the platform and jump-started its renaissance.
* Since [[AppleMacintosh Macs]] have historically had few compatible games, every gamer who owns one is essentially required to get certain games. Some examples are the ''VideoGame/{{Marathon}}'' Trilogy, and anything made by BlizzardEntertainment.
** Preemptively, Valve releasing Steam and the Source-based games on Mac (''VideoGame/{{Portal 2}}'' and ''VideoGame/Left4Dead2'' in particular) have caused a huge jump of interest in Mac gaming. The same thing has happened to [[{{Unix}} Linux]] since the announcement that Valve would be porting Steam to Ubuntu.
* ''VideoGame/TheSims'' can be credited with kicking off the resurgence of casual gaming of the 2000s (along with internet games).
* The ''VideoGame/AgeOfEmpires'' series, ''VideoGame/AgeOfEmpiresII'' in particular, was one of the most successful and well crafted PC RTS games of its time, and still maintains a large player and modding community despite being a decade old.
* The LAMP server (Linux, Apache, MySQL, and PHP) let people build servers using off-the-shelf PC hardware, giving Linux a huge boost in its early days. Along with powering much of the Internet, it quickly became the standard for individually-owned game servers.
* Windows XP only really started to die off in favour of Windows 7 when ''VideoGame/{{Battlefield 3}}'' was announced to be Windows 7/Vista exclusive. ''VideoGame/CallOfDutyBlackOps2'' making the same announcement a year later likely helped as well.
* TelltaleGames singlehandedly resurrected the AdventureGame genre.

* The original ''SamuraiShodown'' on the NeoGeo home console.
* ''MetalSlug'', especially ''3''.

[[folder:Other Systems]]
* PlatformFighter ''Towerfall'' was the closest thing the Kickstarted ''Ouya'' console had to a killer app before ''[[UpdatedRerelease Towerfall: Ascension]]'' came to PS4 and PC.
* The BBCMicro was guaranteed good sales in the education and office market thanks to being [[BackedByThePentagon Backed By The Government]].[[note]]when Creator/TheBBC's educational programming department first got serious about computer science, every manufacturer had their own fork of BASIC that was almost but not ''quite'' compatible with everyone else's, so eventually they realised the only way to have a set of programming exercises that'd work for everyone was to commission a computer designed to their own specifications. Acorn Computers won the contract and the rest is history.[[/note]] But without sales of ''VideoGame/{{Elite}}'', it's unlikely they'd have made much if any headway in the home computer market, much less become as iconic in British geek culture as they are.
* While VideoGame/NetHack is a multi-platform game, just about any serious Unix or Linux user has a copy installed, as it's one of the few decent games available.

* PopcapGames owns the casual genre. Most casual games are tweaked knockoffs of Popcap's efforts, which in turn are just variations of match-3, spot-the-difference, time-management and various simple luck/skill-based physics minigames. Doesn't matter. Popcap owns the entire genre. There are still entire blocks of people who would never call themselves 'gamers' who are obsessed with ''VideoGame/{{Bejeweled}}''.
* ''VideoGame/TeamFortressClassic'' was, for the longest time, THE online shooter. ''VideoGame/{{Counter-Strike}}'' took over, and the market has since fragmented between WW2 and futuristic/modern shooters.
* ''VideoGame/GuitarHero'' turned {{Rhythm Game}}s from [[{{Konami}} weird J-Pop things]] (in the eyes of many) to a major western phenomenon.
* Though it had less casual-appeal than the above, ''VideoGame/DanceDanceRevolution'' kept the arcade scene afloat single-handedly, and no doubt was an inspiration for the physicality of gaming aspects that would become part of the Wii's appeal. Years later, ''Just Dance'' would turn dancing games into a genre in its own right, and incidentally helped Ubisoft become the Wii's biggest supporter outside of Nintendo.
* Do you like RealTimeStrategy games? Then you ''must'' have tried two of BlizzardEntertainment's best games: ''{{Starcraft}}'' and ''VideoGame/{{Warcraft}} III''. Or the ''VideoGame/CommandAndConquer'' series. In the following years, the ''VideoGame/DawnOfWar'' series or ''VideoGame/CompanyOfHeroes'' also count.
* Similarly, do you like [[TurnBasedStrategy turn-based]] FourX? If so, then at least one of the ''VideoGame/{{Civilization}}'' games is probably in your library.
* For {{MMORPG}}s, ''VideoGame/WorldOfWarcraft''. It's the one everyone's heard of, and it has slightly more players than the next 2 biggest (''GuildWars'' and ''Knight Online'') ''put together''. And for browser [=MMORPGs=], it's ''Runescape''.
* Do you like Japanese [=RPGs=]? You probably have a ''Franchise/{{Pokémon}}'', ''Franchise/FinalFantasy'', or ''Franchise/DragonQuest'' game. In fact, ''DragonQuest'' is such a killer app in Japan that even [[SalaryMan Salarymen]] will take a day off and students from the most prodigious schools will cut class just to buy a copy on the day it becomes available for sale.
* While still relatively obscure overseas (except for the ''[[CashCowFranchise Persona]]'' series,) ''Franchise/ShinMegamiTensei'' is right up there with Japanese role-playing games in Japan.
* Do you like Western [=RPGs=]? You've probably played ''Franchise/TheElderScrolls'', series or ''VideoGame/BaldursGate''.
* High fantasy not your thing? Then you've probably got at least one ''VideoGame/{{Fallout}}'' or ''Franchise/MassEffect'' game in your library.
* ProfessionalWrestling has really only had one game that could be considered a killer app - ''VideoGame/WWFNoMercy'' for the N64. No Mercy had a big roster, an in-depth storyline mode, a very detailed for the time create-a-wrestler, many different types of matches, and good multiplayer. Even people who don't like professional wrestling often like ''No Mercy'', and the game still has an active modding community today. The next closest example would probably have to be ''WWE Smackdown: Here Comes The Pain''

* ''VideoGame/Myst'' was '''the''' killer app that transformed the CD-ROM drive from a mildly interesting computer curiosity into an absolute must-have feature.
** Myst '''was''' a killer app for the Mac, as was originally written for the Mac and appeared around the time CD-ROM drives first started becoming standard equipment on Macs.
** When the game was eventually ported to the PC, it also made sound cards a must in every PC. One '''must''' have a sound card to fully enjoy the game, and after the title, any PC that doesn't have a sound card is considered a poor man's PC. Prior to that, sound cards were largely considered a luxury peripheral that is unnecessary for mainstream gaming. It also helps that all sound cards made back then has a built-in SCSI controller, which is needed if you're going to add a CD-ROM drive to the PC because all CD drives manufactured at that time only supported the SCSI interface (mainly because Macs, UsefulNotes/{{Amiga}}s and UsefulNotes/{{Atari ST}}s back then used SCSI for the hard disk and CD-ROM drive, and thus SCSI came as standard on them).
* ''Film/TheMatrix'' is widely acknowledged to be the killer app for the DVD format. Every store front had the hallway assault and the rooftop bullet time sequence playing on the screens and so many people bought their first DVD player with a copy of ''The Matrix'' that the movie might as well have been bundled with the player. It was the first DVD million-seller.
** Also a two-in-one of sorts: The PlayStation2 benefited greatly from having a built-in DVD player. In some regions it was in fact the cheapest DVD player on the market for several months.
** A lot of people also bought DVD players just to use Creator/{{Netflix}}.
** [[BetterOnDVD The ability to blow through entire seasons of TV shows]] in a weekend was also a major selling point for [=DVDs=].
* The UsefulNotes/BluRay format had a similar Killer App: ''Film/{{Avatar}}'' sold 1.5 million copies on its ''first day'', 6.2 million after three weeks. It's also not surprising that the PlayStation3 is the most popular Blu-ray player.
* If you can call an industry a Killer App for one product: The force that turned [=VCRs=] from neat toys to must-have appliances and also settled the [=VHS/Betamax=] format wars? [[TheRuleOfFirstAdopters Porn.]]
** Porn is actually a driving force behind a lot of entertainment-related technological advances (see below.)
* ''WesternAnimation/TheSimpsons'', ''WesternAnimation/FamilyGuy'' and ''Series/{{Firefly}}'' proved that DVD series boxsets were both financially lucrative and did not ruin reruns of regular TV. See also {{Uncancelled}}.
** The case was proved long before ''Firefly'' came along. ''Series/BabylonFive'', for example, made half a billion dollars for Warner Bros several years earlier.
* ''VideoGame/{{Half-Life}} 2'' and Counter Strike Source was responsible for {{Steam}}'s success today, and the popularity of digital distribution as a whole, though that might have something to do with the games ''requiring'' Steam to play.
* What ''Film/TheMatrix'' was to [=DVDs=], {{Music/Dire Straits}}' album ''Brothers in Arms'' was to [=CDs=], as it was the first album to sell over a million copies in the format and the first to outsell the LP version. The albums's insanely high sound quality showed off what those shiny little discs could do.
** {{Music/Pink Floyd}}'s ''Music/TheDarkSideOfTheMoon'' was also a killer app for [=CDs=], as the album's high sound quality had long been used to demonstrate audio equipment. At one point in TheEighties EMI had an entire CD plant dedicated to churning out copies of ''Dark Side of the Moon'', and this was when there were only ''two'' CD pressing plants in the entire world!
* Music/TheBeatles' ''Rubber Soul'', ''Revolver'', ''Sgt. Pepper's Lonely Hearts Club Band'' and Music/TheBeachBoys' ''Pet Sounds'' have been cited as killer apps for albums for pop[=/=]rock music.
* AngryBirds lives on as one of the most popular games for many formats, but ''especially'' for [=iOS=] devices.
* Creator/{{Netflix}} is the killer app for a lot of streaming set-top boxes, including Apple TV and Roku. For many people, the only reason to get a Netflix account was to see their original programming. One show of theirs in particular has become a true killer app: ''Series/OrangeIsTheNewBlack.''
* The resurgence of vinyl's mainstream popularity was spearheaded by Beck's Guero (2005) and Red Hot Chili Peppers' Stadium Arcadium (2006), both of which were explicitly mastered much better on vinyl than they were on digital formats. Many bought turntables just to play them.

* [=NewTek=]'s ''Video Toaster'' was the one selling point of the UsefulNotes/CommodoreAmiga that made said machine popular at video production houses and film studios. ''Deluxe Paint'' was another program that sold Amigas.
* {{Toonami}} is credited with ushering in the mainstream Japanophilia boom of the early-to-mid 2000s, primarily for introducing the anime phenomenon to the west.
** Speaking of Creator/CartoonNetwork, ''What A Cartoon!/World Premiere Toons'' and later, ''CartoonCartoonFridays'' proved to be this as it was a launching pad for the network's original series.
* If one goes even earlier, you can credit Voltron for anime's expansion in the USA and abroad. Its most notable and innovative (at the time of course) feature was the Stereophonic Soundtrack that BeastKingGolion,its original version, lacked. This feature made it THE show to air to showcase the Stereo capabilities of most affiliate stations and systems.
* Let's not mince words: [[TheRuleOfFirstAdopters Porn is the killer app of EVERY new form of communication]], to the point that format wars have been decided based on which one was better for/more accepting of porn. The sole exception might be how porn took up HD-DVD first, which eventually lost out to Blu-Ray. However by the time the war was settled, Sony had made it clear they weren't going to make the same mistake they made with Betamax.
* For the UsefulNotes/AppleII, the killer app wasn't a game at all (though there were an awful lot of those): it was the first electronic spreadsheet, [=VisiCalc=]. And for the IBM PC, it was the spreadsheet program Lotus 1-2-3.
** Spreadsheets seem to get a lot of this: Excel, for example, is Microsoft Office's Killer App. It also helped two [=WIMP=][[labelnote:*]]Windows/Icon/Menu/Pointing Device[[/labelnote]] platforms get off the ground: first, it was one of the killer apps for Macintosh, and a couple of years later (1987) Excel became the main reason to use the fledgling Microsoft Windows.
*** Spreadsheet programs attract the killer app label because the complex financial and statistical functions they enable are exponentially more difficult--sometimes functionally impossible--without the visual/computational assistance of the spreadsheet. Think about how headache- and eyestrain-inducing a complex spreadsheet is (unless you're into that sort of thing). Then imagine ALL the same information presented in a hard-copy ledger. Killer. App.
** [=VisiCalc=] alone was selling ''more'' Apple ][ than all of its games combined, actually, and its need for a screen real estate and RAM was a real driver for the Language Card (which added more memory) and 80-column Card ([[ExactlyWhatItSaysOnTheTin self-evident]]), and a real reason why both these upgrades were later officially incorporated into the motherboard design.
*** Apple would eventually have its own killer app for the //e (and its [=ProDOS=] operating system) with [=AppleWorks=], one of the first integrated software packages (combining a spreadsheet, word processor, and database). Apple didn't even advertise it heavily at first, because they didn't want to step on the toes of their third-party vendors (nor overshadow their own [=AppleWriter=]), but it still sold so well that it even outsold Lotus 1-2-3 for a while. Its later-generation versions, however (sold by Apple-spinoff Claris, spun off to dodge accusations of antitrust violation under the product name [[CaptainObvious [=ClarisWorks=]]], on both Mac '''and''' PC, were eclipsed by Microsoft Office and by Corel's iconic word-processing product [=WordPerfect=].
* Almost all of the killer apps for UsefulNotes/MacOS X are made by Apple. Half of them come with the system.
** Apple originally made a number of killer apps directly on the original Macintosh's launch -- [=MacPaint=], [=MacDraw=], and [=MacWrite=] -- that have been the gold standard ever since for WIMP GUI image editors, drawing programs and word processors. But it was the first WYSIWYG page layout program, [=PageMaker=], that made desktop publishing possible and guaranteed the Mac's most lucrative niche. [=PageMaker=] was also a killer app for UsefulNotes/MicrosoftWindows when it was ported over, before Windows became really popular.
** Apple's OS is the killer app of the {{Macintosh}}, and recently, [[ Parallels]] is a very good killer app for Intel Macs since it makes the "you can't play as many games on a Mac" argument obsolete.
* In America, ''Series/ILoveLucy'', ''Texaco Star Theater'', the Army-[[RedScare McCarthy]] hearings, and the 1960 Presidential debates were television's Killer Apps. In Britain, the coronation of Queen Elizabeth II was this.
** JFK's assassination was also a killer app. Everyone watched the news, and forget about work happening the next day.
** The moon landings were this in, of all places, UsefulNotes/SouthAfrica. When the people of South Africa realized that they were the only people in the Western world who couldn't watch Neil Armstrong take his one small, historic step on the surface of the moon, they pressured their government to end its ban on television programming (which it viewed as [[NewMediaAreEvil a morally corrupting influence]]). They finally lifted the ban in 1975.
** Ironically, for Japan, which was still only barely out of the post-war devastation and overwhelmingly poor ([[MindScrew it was worse there than in North Korea, actually]]) it was ''also'' the Elizabeth II coronation. People were drawing five-year loans with a ridiculously rip-off rates only to be able to watch it.
* In Britain, the killer app for colour [=TV=] was snooker. The 1969 BBC show ''Pot Black'', which showed a single frame of snooker each week, was made to increase the sales of colour [=TV=] sets. Although it was really more of a [[TechDemoGame Demo App]] showing what could be done with colour TV that wasn't possible with black and white. People didn't rush out to buy colour TV sets just to watch the snooker - it took until 1977 for the number of households with colour TV to exceed those with black and white.
** The series produced the all-time infamous quote from commentator Ted Lowe: "And for those of you who are watching in black and white, the pink is by the cushion next to the green".
** In America, ''[[Series/StarTrekTheOriginalSeries Star Trek]]'' was the killer app for color TV, which was also part of why the original series was able to stay on the air as long as it did. While NBC had wanted to cancel it, their parent company RCA wanted to keep it for two reasons: they owned the patent for color TV, and ''Star Trek'' was the primary reason Americans bought them. RCA made more money selling them to ''Star Trek'' fans than NBC lost by not giving its time slot to something else.
* The 1990 Gulf War was [[GallowsHumor proverbially]] the killer app for 24-hour cable news, specifically Creator/{{CNN}}. Where national networks had to eventually return to their regularly scheduled programming after Iraqi phone lines were cut off, CNN had previously had a permanent line installed and continued broadcasting round-the-clock.
* The addition of GPS has been a huge mover for handheld computers. Presumably the medium as a whole is based around the want for calendar and contact programs.
* Taxi work seems to be the Killer App for hybrid cars. No fuel is consumed idling in dense city traffic or waiting for fares, the battery packs are barely affected by massive mileage and indeed seem to thrive on constantly being in use compared to being parked 22-plus hours a day like most personal cars, and both the financial and environmental cost/benefit ratios increase compared to private use.
** Buses fall into this as well.
* The Internet had been around in a form similar to what we use today since at least the early 1980s, but it was NCSA Mosaic, the first easy to use web browser avaialable for [=PCs=] and Macs, that made the network a must-have for computers.
* Bittorrent is the killer app for consumer internet download speed, download caps, and hard drive capacity. YouTube was also a killer app for broadband.
* {{MTV}} was the killer app for cable TV. For sports fans, the killer app was {{ESPN}}.
* {{Unix}}'s killer app, as with UsefulNotes/MacOS, was originally the platform itself, with the ability to redirect input and output at the shell. Another killer app was {{Usenet}}, a precursor to modern social media.
* {{Twitter}}, {{Facebook}} and other social media services are the killer apps for smartphones and tablets.
** Blackberry messenger was a killer app for Blackberry phones, unfortunately for them that changed once cross platform messaging apps appeared in Android and iOS.
* Literature/TheBible was the killer app for the printing press, and with it mass literacy, compulsory education in the Western world, and the Protestant Reformation.
* Guns were part of the reason for the development of interchangeable parts and mass producing.
** If one wants to get a little dark, UsefulNotes/WorldWarII was the killer app for the above as they were applied to firearms, especially after the logistics nightmare that was caused by the lack of these among the Allies' standard Chauchat machine guns back in UsefulNotes/WorldWarI. It's part of the reason the famous Thompson SMG was retired literally right after the war ended - other SMG designs that came about as the war progressed did the job just as well but could be produced at half the cost and much faster.
* Travel. There are some places every tourist will go when traveling to specific cities or countries. Examples can be the Eiffel Tower for France or the Liberty Statue in New York.
** In the past, pilgrimages provided a killer app to make the risks and expense of travel worthwhile -- plus saving your immortal soul! Pious people would make pilgrimages to holy springs, sites of martyrdom, even all the way to the Holy Land -- so in a way, TheBible inspired a Killer App for travel in medieval Europe.
** And, of course, Muslims took pilgrimages to Mecca (and Medina and Jerusalem) before it was cool.
* Some people have suggested invoking killer app when it comes to buying new electronics, namely by testing the hardware by using something that would prove its quality. Specifically, in one article about buying a new television, the reporter suggested taking a DVD of ''Film/MoulinRouge'' to the electronics store with you, saying that if a TV could stand up to its fast pace and bright color palette, it can handle almost anything.
* ''WesternAnimation/SouthPark'' was this to Network/ComedyCentral. When it was picked up, channel viewership was mediocre among cable networks, and there were still cable providers who didn't provide it in their basic package. It created a boom of overall channel viewership and a demand for Comedy Central. Series/TheDailyShow and Series/ColbertReport are also credited with building and keeping audience, but not quite in the same numbers or rate as South Park.
* The getting the UsefulNotes/{{NFL}}'s NFC coverage from Creator/{{CBS}} (as well stealing some of their staff) turned Creator/{{Fox}} from a group of stations that aired ''WesternAnimation/TheSimpsons'' and ''Series/MarriedWithChildren'' into something that it's ancestor Creator/DuMont couldn't: the Fourth Network of American Television.
* The ''Manga/AttackOnTitan'' anime was one for Crunchyroll.