6. Aaron Johnson
You probably saw young Aaron Johnson last in the central role of Kick Ass, but his ability as a character actor has already been exhibited throughout his already long, successful career. He has a seemingly inherent ability to fundamentally change who he is as he clearly displayed with bold take on the legendary John Lennon; as a native of Liverpool myself, I was thoroughly impressed. Its not that hes exactly the perfect face or body fit to play the Joker (then again, neither was Heath Ledger until his costume and make-up were unveiled) but if Nolans Joker proved anything its that the look - in fact, the whole character - is entirely open to interpretation. I imagine Johnson to be a perfect casting choice should a Batman reboot director fancy building a new Joker onto a relatively blank canvas.