All of my historical heroes died young or horribly. Genghis Khan was indeed awesome, but he never relaxed and died in the saddle. Belisarius had his eyes put out by Justinian and died a pauper. Caesar was murdered by his best friend. Tokugawa Ieyasu was under constant threat of assasination. These are fun people to read about, but they would not be fun people to be.

So I guess my answer would be Richard Feynman.