Fred, Kaylee, CJ, Natalie, and Spock are all correct.

Weir is a close second; McKay is right. (Though tomorrow this may change. Or if I think really hard about Weir's breasts.) Cuddy is also a close second (in much the same way). Come to think of it, so is Sam. BtVS I am pretty sure I chose my favorite, but maybe if enough of my friends guess Tara, I'll have to change my mind. :)