Mark Richard Hamill (born September 25, 1951) is an American actor, voice artist, producer, director, and writer. Hamill is best known for his role as Luke Skywalker in the original Star Wars trilogy. But in the voice-over world, he is most well known for voice acting characters such as the Joker in the DC Animated Universe, (primarily in Batman: The Animated Series), Fire Lord Ozai in Avatar: The Last Airbender, the Hobgoblin in Spider-Man: The Animated Series, and Chanukah Zombie on Futurama.
In an interview with IGN a few months ago, Hamill says that Arkham Asylum 2 will be his last time voicing The Joker. Hamill's portrayal of the character is considered to be one of the best characterizations of the villain by many fans.
He almost didn't return to play The Joker in the first Arkham Asylum video game, but when he learned Paul Dini (writer) and Kevin Conroy (voice of Batman) were involved with the project, he changed his mind. His performance in the game wound up winning him much praise from critics.
Now, with Arkham Asylum 2, Hamill says this is really the last time he'll be playing the character, saying, "This will be my last, there's no question about that. But it's the last hurrah."
See his massive list of credits here.