Nothing:
Fried and baked stuff (cookies, pizza, sandwiches, etc etc) mostly give crums and/or greasy fingers.
Candy and chocolate gives shitloads of wrappers (plus chocolate gives crums of well, annoying melting one's).
Fruit and lots leaves pits, shells or whatever crap.
Drinks are too risky, I don't want my keyboard screwed up by some fruit juice or something and I like to keep my desk clean, nor do I want bottles lying around on my room.