Interesting question.

When I was 14, I messed around with my best friend across the street one night. It turned out pretty badly, and we never spoke again. He became a musician, and founded a rock band that was pretty popular on the late 1990s and early 2000s. He had fan clubs, groupies, etc. Though his name will remain nameless, I would say he is likely the most famous person I have been sexual with.

In terms of just seeing a cock, several graduates from my high school have gone on to become writers for well-known magazines such as Scientific American, editor's of well known magazines related to politics and the outdoors, and a TV reporter for Fox News (cough). I guess I have seen some pretty famous willies...