Troy Baker is one of the biggest voice actors in gaming these days. He's been the main voices in Saints Row IV, The Last of Us, BioShock Infinite, and will soon play Revolver Ocelot in Metal Gear Solid V: The Phantom Pain.
All big roles, but probably the hardest one to play has to be The Joker from the upcoming Batman: Arkham Origins. Mark Hamill left some very big shoes to fill, but Troy Baker kills it as the new voice of Joker. Watch him perform the Joker's monologue from The Killing Joke and be amazed.