Carrie Fisher played the nun in Charlie's Angels2.
Michael Sheard, admiral Ozzel, plays Adolf Hitler in Indiana Jones and the Last Crusade.
William Hootkins has a part on the West Wing I think.
Bruce Boa, General Rieekan, had a part in Fawlty Towers, he is the American ordering a Waldorf Salad.
Kenneth Colley plays a part in an episode of Hercule Poirot, as some rich man who fakes his own death and hides as a tramp. He also played a role in a movie about a few people surviving on an island after a plane-crash, and it's not "Lost
".
Ian McDiarmid played a pedofhile in a british detective series, Spooks I think.
Mark Hamill did the voice of Ripburger in the excellen game Full Throttle.