I really hate people who are big-headed and think that they are the best at everything. I have one in my section at work. He doesn't stop talking about 'how great he is' and 'what his greatest accomplishments are' and 'how we are all incompetant engineers and he's the only competant engineer in the section'. One day, someone'll turn around and smack him in the face. Hope it's me who does that.
Also, Peter would like to rant about what really grinds his gears:
http://www.youtube.com/watch?v=_zIzciYwGHM