How about Clive Owen? That guy plays a perfect creep (see Closer).
I have faith in Nolan... Memento, Insomnia and Batman Begins were all thrilling movies.
Heath Ledger?...There are so many other better choices out there. Oh well, I agree with Wolverine on this one, and hope that the direction takes off well as it's predecessor did, "Batman Begins"...In my opinion, I would have chosen Jude Law to be the next Joker. He just has that wierd happy face that would perfect for the character...