That curly haired short guy on Moonlighting, who was in Revenge of the Nerds. Ughhh! (I looked him up, actor named Curtis Armstrong). Hated him on that show!
Also Goren on the 1st season of Law and Order Criminal Intent. I still cringe watching him - the ultimate know-it-all. What a show-off he was - he was always right, pretending to be so "humble". ICKKKK. He got less conceited and less annoying in later seasons, though - I enjoyed those seasons better.