I voted for Dicaprio, but honestly it's almost a tie between him and Nicholson. There are so many great performances in that movie though. I especially love Mark Wahlberg's and Alec Baldwin's performances. Before that movie I honestly can't remember a single film that had me laughing so hard that wasn't a straight up comedy and the combination of Nicholson, Wahlberg and Baldwin had a lot to do with that.