Breakthrough Hit

This is the very work that practically begins the career of a creator. This is the hit that gives the creator success in their medium. This is the Breakthrough Hit.

You can bet that any creator who you can name off the top of your head has his/her Breakthrough Hit. For some creators, it could be the very first work he/she created. For others, it comes only after a series of unsuccessful attempts, although these early attempts stand a chance of being Vindicated By History. For many Breakthrough Hits, creators are often subject to the curse of Tough Act to Follow, as practically every subsequent work may be compared to the Breakthrough Hit.

Compare Killer App (equivalent for game systems) and Star-Making Role (equivalent for actors). Compare and Contrast Magnum Opus, another landmark in a creator's career. There may be some overlap for a few creators, but Magnum Opus usually represents the pinnacle of the career while Breakthrough Hit represents the beginning. Contrast Creator Killer and One-Hit Wonder.

Anime and Manga

 * Zombie Powder for Tite Kubo in his own country, Bleach worldwide. Likewise, Butsu Zone for Hiroyuki Takei country-wide, Shaman King internantionally''.
 * Ouran High School Host Club for Bisco Hatori; prior to it, she had written some shojo which was never well-known.
 * Dr. Slump for Akira Toriyama in his home country. He would later make it big worldwide with Dragonball.
 * Gun Buster for Hideaki Anno.
 * Love Hina for Ken Akamatsu.
 * Naruto for Masashi Kishimoto.
 * Yu-Gi-Oh for Kazuki Takashi, Yu-Gi-Oh Duelist worldwide.
 * Puella Magi Madoka Magica for Gen Urobuchi

Comics

 * Action Comics #1 for DC Comics, which featured the debut of Superman.
 * The New Teen Titans for Marv Wolfman.
 * V for Vendetta for Alan Moore.
 * Chris Claremont and John Byrne, The Uncanny X Men
 * Jack Kirby, Captain America
 * Stan Lee, The Fantastic Four
 * Steve Ditko, The Amazing Spider Man.
 * Frank Miller, Daredevil
 * John Buscema, The Avengers.
 * Kurt Busiek and Alex Ross, Marvels
 * Jim Lee, The Uncanny X Men
 * Mark Waid, The Flash
 * Neal Adams, Batman
 * Jim Steranko, Nick Fury Agent Of SHIELD.
 * Brian Michael Bendis, Ultimate Spider Man and Daredevil.
 * Grant Morrison, Doom Patrol and Animal Man
 * Neil Gaiman, The Sandman
 * Scott Snyder, American Vampire

Film - Animated

 * Snow White and The Seven Dwarves for Walt Disney in the feature-length animated film industry.
 * After breaking away from Disney, Don Bluth had his breakthrough with The Secret of NIMH.
 * Toy Story for Pixar.

Film - Live Action

 * The Terminator for James Cameron
 * American Graffiti as a director and Star Wars Episode V: The Empire Strikes Back as a producer for George Lucas.
 * Jaws for Steven Spielberg.
 * Alien for Ridley Scott.
 * The Lord of the Rings for Peter Jackson.
 * Pulp Fiction for Quentin Tarantino.
 * The Godfather for Francis Ford Coppola.
 * Taxi Driver for Martin Scorsese.
 * Carrie for Brian De Palma.
 * Clerks for Kevin Smith.
 * Romancing the Stone for Robert Zemeckis.
 * Halloween for John Carpenter.
 * Rosemarys Baby for Roman Polanski.
 * Animal House for John Landis.
 * The Usual Suspects for Bryan Singer
 * Pi for Darren Aronofsky
 * Memento for Christopher Nolan

Literature

 * The Da Vinci Code for Dan Brown.
 * Twilight for Stephenie Meyer.
 * Tortilla Flat for John Steinbeck.
 * Nightfall for Isaac Asimov. As he himself described it "The writing of 'Nightfall' was a watershed in my professional career ... I was suddenly taken seriously and the world of science fiction became aware that I existed. As the years passed, in fact, it became evident that I had written a 'classic'".
 * The Hobbit for JRR Tolkien.
 * The Lion the Witch And The Wardrobe for CS Lewis.
 * Ender's Game for Orson Scott Card.
 * The Andromeda Strain for Michael Crichton
 * The Hunger Games for Suzanne Collins.
 * Carrie for Stephen King

Live Action TV

 * All That for Dan Schneider.
 * Law and Order for Dick Wolf.
 * Buffy the Vampire Slayer for Joss Whedon.
 * CSI for Jerry Bruckheimer.
 * Veronica Mars started Rob Thomas' career as a television producer, although his book Rats Saw God started his career as a novelist.
 * Heroes for Tim Kring (although his previous series Crossing Jordan lasted longer).
 * Magnum PI for Donald Bellisario

Music

 * "Love Me Do" for The Beatles in their home country. Their international breakthrough would be "I Want to Hold Your Hand".
 * "Just Dance" for Lady Gaga, after several years in the business and a shift from being a piano-pop-type singer/songwriter
 * "Run It!" for Chris Brown.
 * The album Off the Wall and its lead single "Don't Stop 'til You Get Enough" codified much of what made Michael Jackson famous, helping establish him as the definitive musician of The Eighties. He was already noted as the lead singer of the Jackson 5, and already had a solo career started even while he was with them, but Off the Wall established what he would be known for for many years to come.
 * "You Really Got Me" for The Kinks, who, prior to this, had two unsuccessful singles.
 * Elton John's Self-Titled Album and "Your Song" were his breakthroughs. His first album, Empty Sky, was unsuccessful.
 * "Born to Run" for Bruce Springsteen.
 * Pink Floyd hit it big with the album The Dark Side of the Moon. For a specific song, "Money" is probably the best fit.
 * "Piano Man" for Billy Joel.
 * Supertramp's first two albums were commercial failures, and then Crime of the Century was released to commercial and critical acclaim, with "Dreamer" being a major hit.
 * "White Liar" for Miranda Lambert. Her first two albums had modest hits but impressive sales; "White Liar" was her first #1 and kicked her career into high gear.
 * After a dud of a first album, Tim McGraw broke through with his fourth single, "Indian Outlaw", and never looked back.
 * "She's Got It All" was the first big hit for Kenny Chesney, who had three albums' worth of modest hits before it.
 * "Somebody Like You" for Keith Urban. His first album produced a #1 in "But for the Grace of God", but the song is long since forgotten (partly since "Somebody Like You" was, per Billboard, the top country hit of 2000-2010).
 * 1972's "Starman", a last-minute addition to The Rise and Fall of Ziggy Stardust and the Spiders from Mars (because RCA wanted a song they could push as a single), finally established David Bowie as a topflight act after four previous albums and only one Top 5 hit -- he'd been recording since 1964.
 * "Drink in My Hand" by Eric Church. Although his albums and singles sold well, Church had never seen Top 40 on the Hot 100, and had just barely gotten into the Top 10 on the country charts. "Drink" became his first #1, and "Springsteen" took off like a rocket immediately afterward.

Tabletop Games

 * Magic the Gathering for Richard Garfield and Wizards of the Coast
 * Dungeons and Dragons for Gary Gygax.

Theatre

 * Joseph and The Amazing Technicolor Dreamcoat for Andrew Lloyd Webber.

Video Games

 * Donkey Kong for Nintendo (and Shigeru Miyamoto). Super Mario Bros would later be their breakthrough in the console games business.
 * For Nintendo's sub-companies: Donkey Kong Country for Rare (before they were bought by Microsoft), Kirbys Adventure for HAL Laboratory, Metroid Prime for Retro Studios.
 * The original Sonic the Hedgehog for Sega and Sonic Team. Before then, Sega remained in the shadow of Nintendo as a console developer.
 * Half-Life for Valve Software.
 * Final Fantasy I for Square. Before then, they were just a struggling company who couldn't make a hit.
 * Dragon Quest I for Enix, the JRPG juggernaut's other half.
 * Halo for Bungie (and for Microsoft in the game business). Bungie did make several games before, most notably the Marathon series, but didn't achieve mainstream popularity before Halo.
 * Warcraft: Orcs and Humans for Blizzard.
 * Bejeweled for Pop Cap Games.
 * Crash Bandicoot 1996 for Naughty Dog.
 * Spyro the Dragon 1998 for Insomniac Games.
 * Disgaea Hour of Darkness for Nippon Ichi Software.

Web Original

 * Yu-Gi-Oh the Abridged Series for Little Kuriboh.
 * The Angry Video Game Nerd for James Rolfe

Western Animation (Excluding Film)

 * Steamboat Willie for Walt Disney.
 * Dexters Laboratory for Craig McCracken and Genndy Tartakovsky.
 * The Fairly Odd Parents for Nickelodeon animator Butch Hartman.
 * Batman the Animated Series for Paul Dini and Bruce Timm.
 * Gargoyles for Greg Weisman.
 * John Kricfalusi had a long career before then, but The Ren and Stimpy Show is what made him truly famous.
 * The Simpsons for Matt Groening and for the FOX network.
 * South Park for Trey Parker and Matt Stone.
 * Family Guy for Seth Macfarlane.
 * Johnny Bravo for Van Partible. It also gave a start to the aforementioned Seth Macfarlane and Butch Hartman (as well as Steve Marmel) in the art of writing.
 * Johnny Test for Scott Fellows.
 * Gerald McBoing-Boing for UPA.
 * My Little Pony Friendship Is Magic and/or Transformers Prime for The Hub network.