Aiden Mercer
Part Man, Part Machine, All Badass
And what of Mark Hamill when he played c#ck-knocker on Jay and Silent Bob Strike back? Come on! He was a superb villain in that film, even though that entire scene with him in character was nothing but a badly made rip-off of Star Wars. But yes, other than that, I do believe he is the best voice actor for the Joker (you can't beat Ledger in actual films for Joker though).