Cult Soundtrack

This is music in a film which becomes one of its major selling points or unique identifiers. Generally regarded as a Crowning Music of Awesome, this music really helps a number of cult films keep a profile through the decades and is often the thing that people mean when they defend it with talk about its "atmosphere".

Particular causes for such a soundtrack may be the use of a single popular band or musician for the soundtrack in contrast for using a score composer or using many songs from different sources.

It is the existence of several Cult Soundtracks from the late 70's and 80's that lead to the more modern practise of focusing on getting a soundtrack and movie tie in for mutual publicity that leads to today's Breakaway Pop Hit phenomenon.

Compare Just Here for Godzilla. A clue to spotting one of these is when the soundtrack announcement for the sequel leads to And the Fandom Rejoiced.

Anime

 * Cowboy Bebop fans have two sections of their brains. One section is for enjoying the quirky and engaging character, intriguing aesthetics and well-developed universe. The other section is for the music which is a sound unlike most other anime and musical director/composer Yoko Kanno given as a reason to watch the show equal to everything else. It is observed through MRI scans that the bigger the fan, the more engorged the latter section of the brain.
 * To a degree, this applies to almost everything Yoko Kanno has a hand in. Evidence suggests she may actually be God.
 * To a lesser extent, FLCL's soundtrack by The Pillows.

Film

 * Queen's Flash Gordon film soundtrack and A Kind of Magic, an unofficial soundtrack album album for Highlander (using six out of nine of the album's listing). Flash Gordon and Highlander were quite kitsch and dated in their own way but the songs gave them both something memorable that people could look back fondly on and which nearly always get brought up in critiques.
 * Xanadu became a cult film in large part because of its soundtrack.
 * Kevin Smith's debut Clerks probably would not have been nearly as successful had he not ended up with a soundtrack filled with various alternative, grunge and punk bands. Most of the budget went towards getting rights for the music.
 * Until the End of The World- In 1991, Nick Cave and the Bad Seeds, Elvis Costello, REM, Depeche Mode, and a number of other artists were asked by Wim Wenders to make for his Twenty Minutes Into the Future piece the kind of music they thought they'd be making in the year 1999 as the world was about to end.
 * Transformers the Movie includes the synthesised score by Vince DiCola and notable songs such as "Dare To Be Stupid" by Weird Al Yankovic and "The Touch" by Stan Bush have received a certain cult status amongst popular culture and the soundtrack has been re-released and remastered several times.
 * The rather forgettable 1993 thriller Judgement Night mostly drew attention for its innovative Rap Metal soundtrack, which included collaborations between famous Alternative Rock and Heavy Metal bands (Sonic Youth, Helmet, Pearl Jam, Mudhoney, Biohazard, Slayer, Living Colour, Dinosaur Jr, Therapy?, Teenage Fanclub, Faith No More) and Rap groups (House of Pain, Cypress Hill, Sir Mix-A-Lot, Fatal, De La Soul, Run DMC, Onyx, Ice-T, Del Tha Funkee Homosapien, Boo-Yaa T.R.I.B.E.).
 * Message boards would have you believe that How to Train Your Dragon's soundtrack is its key accolade. John Powell's score has certainly developed a rabid fanbase.
 * As well received as the film O Brother Where Art Thou was, one of its greatest achievements was to bring Old Time, Roots and Bluegrass Music back into the public ear. Its soundtrack album is legendary, having topped the album charts, sold over 7 million copies in the United States alone and won countless awards (including the Grammy for Album of the Year).
 * Tim Burton's film soundtracks have an extensive cult following. Or, rather, Danny Elfman's work as composer has a cult following.
 * Mean Guns. You don't believe how many threads in Russia and Ukraine music search forums are dedicated to finding at least something from the film's score. Though the film itself also has a dedicated fanbase.
 * The Phantom of the Paradise soundtrack, especially in Winnipeg, Canada where it went gold.
 * Hackers' soundtrack was a sampling of techno, rave and electronica in the nineties when rave was near its peak, though the most famous was The Prodigy's "Voodoo People"; it went on to have two more volumes.
 * Pi's soundtrack, arranged by Clint Mansell, set the scene for its hallucinogenic plot. Pi r^2 is more famous than the film it was made for.
 * This seems to be the pattern with Clint Mansell's film scores in general. Requiem for A Dream, The Fountain, Moon (2009)...
 * Opinions are divided when it comes to the quality of Tron Legacy, but most folks agree that the soundtrack Daft Punk cooked up for it is a level of perfection Clu would sign off on.
 * Conan the Barbarian (1982) composed by Basil Pouledouris, is famously known for causing hair to grow on listeners in previously unknown places, along with causing heavy metal fans to develop a hankering for classical music. It's also considered one of the all-time great soundtracks, despite the film itself being a total Camp Classic.
 * Lost Highway and Natural Born Killers featured soundtracks compiled by Trent Reznor.
 * The Social Network (co-written by Reznor) too.
 * Cool World is largely panned, but its soundtrack, featuring industrial rock, electronic and pop songs, is a cult favorite.
 * End of Days, likewise, was largely forgotten, but the soundtrack is noteworthy for featuring off-album tracks by Rob Zombie, Powerman 5000, Everlast, Eminem, Sonic Youth, Korn, Limp Bizkit and Guns N' Roses.
 * The scores to films by John Carpenter are quite often a large part of their cult appeal.
 * Amelie's soundtrack, composed by Yann Tiersen, received rave reviews and even went platinum in Canada.
 * While Space Jam's quality is debatable, to say the least, many consider its soundtrack to be one of the most underlooked albums of the 90's. Hit Em High (featuring B-Real, Method-Man, Coolio, LL Cool J, and Busta Rhymes,) in particular, is considered to be one of the most overlooked songs ever (at least based on by many YouTube commenters.
 * Don't forget about the Space Jam's theme song, with it constantly being mashed up with what seems like almost every other recorded piece of audio.
 * Singles was a forgettable Cameron Crowe romantic comedy, but its soundtrack was a huge hit. This due to the movie being set in Seattle and the soundtrack (and film) containing many of the stars of the then-nascent so-called "grunge" movement.
 * Heavy Metal is well-regarded for its soundtrack featuring artists such as Don Felder, Blue Oyster Cult, Black Sabbath, Cheap Trick, Sammy Hagar, and Devo. Even though the music rights kept the film from getting a home video release until 1997, the soundtrack has constantly been in circulation since the film was first released in 1981.

Live Action TV

 * Battlestar Galactica Reimagined gained as much praise for the score by Bear McCreary as it did for its diverse characterization, engaging plot, and high production values. For example, when the Season 4 album was released in July 2009, the only albums that outsold it upon release were of Michael Jackson.

Video Games

 * Guile's Theme goes with everything.
 * Frank Klepacki's soundtracks for the Westwood RTS games Dune II, Command and Conquer, etc.
 * Several video game composers have the ability to turn heads simply by having their names attached to a game; some prominent examples are Nobuo Uematsu, Michiru Yamane, Yasunori Mitsuda, Akira Yamaoka, Hitoshi Sakimoto, and Manabu Namiki.
 * Ar Tonelico, it may have a silly plot and over the top fanservice and innuendo, but it has a beutiful soundtrack. There's a heavy emphasis in music and song in the game since the magic is all Magic Music. The developers even went so far as to make a whole fictional language and several dialects with people singing them like here
 * Many NES games are known for their soundtracks - many more gamers are familiar with the theme tunes to Super Mario Bros, The Legend of Zelda and Metroid than have actually played the games from which they originated.
 * Touhou. The sheer number of fan-made remixes and arrangements of the series' music is staggering, and a large portion of the fanbase is into the games simply for those songs.
 * Both the Japanese/European and the American soundtracks to Sonic CD are regarded this way, though opinions vary as to which is better.
 * Sonic the Hedgehog 2006 is known for two things: being one of the worst Sonic games ever, and having one of the best soundtracks of any Sonic game ever.
 * Jet Set Radio just wouldn't be the same without Hideki Naganuma's music, which could easily stand just as well on its own.
 * Weird Snark Bait example: the mindbogglingly cacophonous "music" for Crazy Bus has been subject to this. It helps that it's the only thing of real noteworthiness, as the gameplay itself simply consists of driving from one end of the screen to the other.
 * Journey to Silius, a game just barely rescued from the scrapheap after the company lost the license the game was originally based on, is generally remembered solely for its soundtrack.
 * Donkey Kong Country: While The Prerendered Graphics might have aged poorly, its soundtrack still has quite a following to this day.
 * Grim Fandango: The soundtrack by Peter Mc Connell is made up of a mixture of Film-Noir style jazz and mexican folk music, perfectly matching the game's aesthetic. While it's hard to find, many fans offer free downloads to others as a way to Keep Circulating the Tapes.
 * Deus Ex featured music composed by Alexander Brandon, Michiel van den Bos, Dan Gardopée (who were responsible for the equally cultic Unreal Tournament and Jazz Jackrabbit OS Ts) and Reeves Gabrels.
 * The songs at the end of Portal and Portal 2 have become very popular.
 * Chrono Cross - the game itself is divisive, but the soundtrack is regarded by almost all who hear it as one of the best in the history of video games.
 * The Silent Hill series came to be known for its soundtracks as much as anything else - which is why the departure of composer Akira Yamaoka from Konami was seen by many fans as the final nail in the series' coffin.

Western Animation

 * Adventures of the Galaxy Rangers had music by John Van Tongeren and Peter Wetzler with tracks sung by AOR bands FM and Refugee (cult bands in their own right). When Koch Vision was asking the fan list for DVD extras, the unanimous vote was for the soundtrack.
 * The sparse amount of music in My Little Pony Friendship Is Magic has apparently been enough to inspire an entire genre of fan remixes, including a Guile-style soundtrack for the much-anticipated fighting game My Little Pony: Fighting Is Magic.