Yoda is the most legendary Jedi in the Star Wars universe. He is timeless and the wisdom and knowledge he possesses is invaluable. He also is known for his 'backwards' speech patterns.
In all of the live-action films, Frank Oz has provided the voice. Tom Kane has been the 'animated' or 'video game' voice of Yoda. Muppet Babies star, Greg Berg dubbed the voice of Yoda in one episode of Muppet Babies.