Underrated/underseen Actors?

One of my favorite actors of all time is Jon Polito, I think the guy had a great screen presence, but outside of the Coen. Brothers stuff he really never got too many sizable roles. (And by the by, what a run of great character actor parts that is he had with the Coens- from his impotently raging mob boss in Miller's Crossing to his meek, colorless accountant in Barton Fink, to delivering the saddest pick up attempt ever committed to film [and directed at Billy Bob Thornton!] in The Man Who Wasn't There) Any others anybody's partial to?