The scene between (actors) Jack Nicholson and Tom Cruise in which Tom tells Jack "I'm not your son, and you're under arrest, you $#%#%@^!" is a good one. I forget the name of the film though.

Another one is the scene in the movie Julius Caesar (maybe based on some classical novel about him, possibly by Shakespeare?), which occurs just before his death. Powerful performances by both the actor playing Caesar and other Roman officials of the time.