Ed Begley, Jr
Ed played Dr. James in Kingdom Hospital, Lars in A Mighty Wind, Henry Starling in Voyager, Jack in Renaissance Man, Greenbean in Battlestar Galactica, and let's not forget She-Devil. With over 200 different credited movies and tv shows to his credit, you can see him all over the place.
I saw him at the Omaha Home and Garden Expo in February 2008. He was so knowledgeable, and a really nice guy. He was surprised I remembered his Voyager episodes, as nobody seems to remember him from there. What can I say? I'm a geek. :D
Ed's offical website.