Characters that try to be too edgy in an otherwise light-hearted enviroment or setting. Not to say they can't be an ass, that I like. I meant that more as in terms of 'Why the hell are they bringing up their past, wangsting all over the place, all because someone dared talk to them?'. This is slightly gone up in ranks due to being a GM now, but even as a player I hate seeing that. I don't really want to see your edgelord 2000x backstory in every single post, and it isn't fun for anyone when your character actively repels every conversation/half the cast. We kinda want this to be a cohesive, albeit quirky group. Hating one guy is fine, but when half the PC's are against you it's gone maybe a bit too far.

Or asspulling/breaking character by using OOC knowledge. Those are amazingly annoying to.