Where the Buffalo Roam- I'm not sure whose Hunter S. Thompson I like better. I think Bill Murray's is better going on voice alone, but Johnny Depp was better with expressions and mannerisms. Both actors' attitude problems reputedly date to their character study of Hunter S. Thompson. Great writer and interesting guy overall, but he spawned this disease of wannabes who can't differentiate drugged-out insanity from pathetic deliberate wackiness.
American Splendor- I really like Harvey Pekar. Paul Giamotti was perfect for the role.
http://www.youtube.com/watch?v=D0akXKxbflM