Jack Benny
Here's a neat clip of comedian Jack Benny performing the first movement of Bach's Concerto for Two Violins in D minor with renowned violinist Isaac Stern. Jack Benny is performing the second violin part which is form Suzuki Book 4 and Isaac Stern is playing the first part from Suzuki Book 5. Benny's antics make it appear that he doesn't know what he is doing, but as you can see he keeps up fairly well, though not quite at Stern's level. To quote Jack, "Can you tell the difference?"
Steve Martin
Most people know Steve Martin for his comedic antics in movies like The Jerk or Father of the Bride. But he's also a heck of a banjo player, too. He's currently touring with the bluegrass band, the Steep Canyon Rangers. Here's a clip of them playing together on the Late Show with David Letterman.