My favorite actor of all time.
Old favorites of his are Five Easy Pieces, Chinatown of course and Batman
More recent As Good as It Gets (on my top 5 movies of all time list), Something's Gotta Give and the Departed.
There's a lot of plain uninteresting movies he was in but his performance, which I later discovered is always based on his normal self, makes it worth the watch. About Schmidt is a good example of those.