Introduction
Martial arts are codified systems and traditions of combat practices, which are practiced for a number of reasons: self-defense, military and law enforcement applications, mental and spiritual development; as well as entertainment and preservation of a nation's intangible cultural heritage.
However, when it comes to fiction, many characters usually break through the regular limit and reach the level of Superhumans. While Martial Arts are not that much of a relevant ability strictly speaking from Superhuman standards, it can become quite useful if other abilities or power sources are incorporated in them (Example being using Acupuncture with it or raising the level via Statistics Amplification like Mori Jin, Reversing back physical strikes back at the opponent like Garou, etc.)
Long story short, while this skill is very common when it comes to fiction, one can still incorporate various other abilities and use it as creatively as possible.
Users
Several characters from Tekken and Street Fighter (verse)
Bang, Garou and several other characters from OnePunch-Man
Most of the characters from Dragon Ball
Most of the Characters from Naruto
Several characters from The God of High School