It really is a testament to the quality of the movie's writers that almost every character was at least "good", considering the size of the cast. I'm trying to come up with a list of who I felt were best but in the end they all kind of just hit the right notes for me.
All except for Wanda. She wasn't particularly bad or annoying, but they really ****ed up trying to give her that accent, imo. She sucks at it, and it brings down the rest of her acting ability (not that she's a particularly amazing actress to begin with).