Answer: Mark Hamill
In 1977, Mark Hamill became a household name with the release of Star Wars Episode IV: A New Hope . Millions of moviegoers of all ages came to associate Hamill with the fresh-faced protagonist played in the series, Luke Skywalker. Despite his best efforts to be typecast as a result of his iconic role in the blockbuster series, it was difficult for Hamill to escape his legacy as Luke Skywalker and secure roles in live action films or television.
As a result, he first tried his hand at stage acting but, despite the praise garnered on the stage, ultimately returned to voice acting. Prior to his Star Wars fame, he'd voiced characters in the I Dream of Jeannie cartoon spinoff Jeannie as well as The New Scooby-Doo . After various but short-lived acting gigs throughout the 1980s, he returned to voice acting as The Joker in Batman: Mask of the Phantasm and Batman: The Animated Series .
His work as The Joker was so critically acclaimed and loved by fans that are busy doing The Joker's voice in multiple series, animated movies, video games, and other media in the 2000s when, bringing things full circle, he reprised his role as Luke Skywalker in the new Star Wars movies starting with 2015's The Force Awakens
Nonetheless, while best known in person as Luke Skywalker and by voice as The Joker, Hamill has voiced in Incredible number of characters over the last thirty years — if you have some time to kill, take a stroll through his IMDb credits and marvel at how many times you've heard him without realizing it.