Firstly I vote for Mental because of his puerile obsession with making himself feel better than everyone else.
Secondly I second Winged's nomination that FuMannChu is a pretty immature guy. In the intelligent debate, he claimed that he places a girl's intelligence at a higher priority than her looks, but I honestly have not seen him do or say anything to back that up. If anything, he completely negates how he claims through his own actions.