Prominent Portrayals in Video Games
Although normally listed as "Ansatsu-ken" (Assassination Fist) in Japanese media, the fighting style of many of the prominent characters in the Street Fighter universe such as Ken Masters, Ryu, and Akuma, is actually a blend of several martial arts styles, but uses a form of karate as the base. Ansatsu-ken is more of a way of choosing specific moves from other styles that work best, similar to Jeet Kune Do, but with more of a focus on techniques designed to kill (at least, before Gouken taught the less deadly versions to his students). In western media for many years, these characters' style was given as "Shotokan Karate".
Dan Hibiki is also seen practicing an art he calls Saikyo-ryuu (The Strongest School), which is a blend of the few techniques he had learned from Gouken before being expelled, plus his father's Muay Thai. As Dan is a weaker character overall than the rest of the cast (with exceptions), his moves are usually much less effective versions of the Ansatsu-ken users.
Art of Fighting
Takuma Sakazaki is the foremost master of a fictional karate style, Kyokugen, which is based on famous real-life karate master Mas Oyama's Kyokyushin style. Takuma has taught this art to his children, Ryo and Yuri, as well as Ryo's best friend, Robert Garcia. Ryo later teaches his student, Khushnood Butt, this style. Aesthetically, Kyokugen is similar to Street Fighter's Ansatsu-ken, but differs in many ways. Dan Hibiki's Saikyo-ryuu (above) is a parody of Kyokugen.
The Mishima family practices their own style of karate, Mishima-Ryuu Kenka Karate. All blood members of the clan except for Lars Alexandersson have used this art, as well as Angel. However, Jin Kazama later purged himself of as much of this style as he possibly could, instead replacing his fighting art with a more traditional karate.
The second Kuma, as well as Panda, utilize a fighting style known as "Heihachi Style Advanced Kuma Shin Ken", which was taught to them by Heihachi and largely utilizes many of Heihachi's Mishima karate techniques.
Fishman Karate is a specific form of karate practiced by the aquatic anthropomorphic characters of the One Piece universe. It utilizes water as a strengthener, which includes the water inside nearly all living beings, making it particularly devastating even on characters who are normally resistant to blunt attacks. On land, it is quite powerful, but when used underwater, Fishman Karate is amongst the deadliest fighting styles of the One Piece series. Although practiced almost exclusively by fishmen, it can be taught to other species, as Koala, a human, has been shown to utilize it.