AFC East
Patriots: Conspiracies and "They hate us 'cuz they ain't us"
Bills: #BillsMafia
Dolphins: I honestly can't say many bad things about their fans (that I've experienced), but Don Shula is the worst.
Jets: Fireman Ed
AFC North
Ravens: "Ineligible receiver formations were CHEATING!"
Steelers: "How many Super Bowls has your team won?"
Browns: "I really think [insert QB name here] can win us games!"
Bengals: The stupid "WHO DEY?" chant.
AFC South
Titans: GO TITANS GO!
Texans: Unhealthy obsession with JJ Watt.
Jaguars: Like the Dolphins, there's nothing in particular about them that annoys me. Those helmets are ugly as hell though.
Colts: "Deflate"
AFC West
Broncos: Not a widespread thing, but I've seen quite a few fans on Twitter that believe Manning and Elway are top 3 QBs in NFL history.
Chargers: Bolo ties.
Raiders: The fact that by simply wearing a Patriots jersey anywhere near the Oakland Coliseum I have a high chance of being stabbed.
Chiefs: That guy air-humping near the Patriots fan.
NFC East
Giants: "18-1! 18-1! 18-1!"
Eagles: The fact that by simply wearing a Patriots jersey anywhere near Lincoln Financial Field I have a high chance of being stabbed.
Cowboys: Feeling the need to defend Tony Romo vehemently if you remotely criticize him.
Redskins: "It's not racist!" (PSA: I don't think the Redskins name is awful [although surely they could change it] but the people who argue that it isn't remotely derogatory are just as bad as the random people who are "offended" by it.)
NFC North
Vikings: I haven't really encountered anything horrible with the Vikings fan base. I guess anyone who defends Peterson's actions annoy me.
Packers: The custom "Owner" jerseys I always see people wearing.
Bears: The Super Bowl Shuffle.
Lions: Any Lions fan who defended Suh / Raiola last year. (Credit to the Lions fans though, 99% didn't do that.)
NFC South
Falcons: "RISE UP!" after every tweet.
Saints: "WHO DAT?" chants.
Panthers: I've ran into Panthers fans who claim that they would've won the Super Bowl if not for Spygate, so those fans are the worst.
Buccaneers: I dislike how it seems they never have a sold out stadium. Sure, the team isn't the best, but you should still support them. Granted, I have no clue what a ticket goes for in Tampa, so that might have something to do with low attendance.
NFC West
Seahawks: The 12th Man jerseys.
49ers: Not much bad I can say, although I hate Jed York. Does that count?
Cardinals: "Patrick Peterson is a top 3 CB! He's underrated" (He isn't.)
Rams: When I was in 3rd grade I let someone borrow a football that had a Patriots logo on it when I was at his house. He moved away a month later and never gave it back or bothered to tell me he was moving. I will hate the Rams and their fans forever for that.