Some have called Ed Witten the smartest man alive today. He is often compared to Einstein, and is by far the most famous string theorist around. Sean Carrol of Preposterous Universe reports (via Not Even Wrong):
Princeton professors stage “filibuster” against the anti-filibuster machinations of alumus Bill Frist. Two of the filibusterers are physicists Chiara Nappi and Ed Witten, the latter of whom regaled the crowd by reading selections from Griffith’s Introduction to Elementary Particles. Couldn’t he have just given an introductory lecture on twistors and string theory?
More here.