Shawn Spencer. Because at the end of the day, he's happier, has actual friends, and romantic relationships that aren't nearly as cringe-worthy as Sheldon's. (And if we're talking a traditional fight, Sheldon has all the muscle tone of a wire hanger, and no coordination whatsoever. Shawn's at least normal-to-upper level slacker fitness and fighting skills, I think.)
Richard Nixon or Chairman Mao. Assume both to be in their "prime".