12. His jokes are topnotch.
Did we mention Sheldon's a comedian, too? The man has a joke for every occasion and he knows when to whip 'em out.
Word to the wise: prepare for a possible spit-take if you happen to be tossing back a cold one when he busts out a one-liner like this: "A neutron walks into a bar and asks how much for a drink. The bartender replies, 'For you, no charge.'"