I'll break your 5 hero limit, as did pg, our local demihero. ;-)

My list is heavy on scientists and philosophers, since I especially admire the ones who changed the way we think (for the better, IMHO).

Socrates

Epicurus

Diogenes the Cynic

Sun Tzu

Shen Kuo

Machiavelli

Leonardo da Vinci (the Shen Kuo of the West! ;-)

Galileo

Kepler

Hume

Darwin

Swift

Franklin

Jefferson

Nietzsche

Sun Yat-sen

Wittgenstein

Feynman

Sagan