One more thing -
Jonah Hill as Samwell (if he can pull off a serious role)
Paul Giamatti as Lord Varys (he plays a good 'funny/sinister')
That guy that played the human torch as Bronn maybe?
Also, is it me or wouldn't it be great to watch Tywin and Stannis in a game of chess? At least until one of them cut the other's head off