Robin Williams as the Joker
According to The Movie Blog,
in a recent interview, Robin Williams said he would love to work with Chris Nolan (Batman Begins Director and he worked with Williams on Insomnia) again. He also directly said he would love to play the Joker. His exact words were "Oh God Yeah!".
Please, God, NO!
Sure he can play a psycho, Insomnia and One Hour Photo proved that, the problem is they were both Robin Williams playing a psycho. Like so many comedian actors, he rarely has the depth to make you forget he is Williams.
My vote for the Joker is Bruce Campbell. You might throw my argument about Williams back in my face, but one viewing of Bubba Ho-Tep would show you how well Campbell can slide into another persona when the part is right.
Plus, he has the chin!