I have a few I wanted to nominate in some sports:
American football-wise, I've had miserable experience with Cowboys and Raiders fans. Eagles fan is up there, but I never really run into them.
I've realized a good majority of the people who cheer for the Cowboys and the Raiders could only brag about how many Super Bowls they won in the past and how great their owner is, and disagreeing with them and they will ALWAYS accuse you of being jealous of their success in the past, and usually any sort of discussion just stops and becomes a shitfest.
Football-wise, I've never really liked ManU fans, because most of them I run into a foreign, who have never been in the UK, or anywhere near Manchester for that matter, and goes on to brag about how great THEIR team is. The bandwagoning is officially huger than America's debt, sad to say.