There's a lot of stuff that drives others nuts that I just don't care about, but the one thing that consistently irritates me is that "chip on the shoulder" guy. The "tough guy" who's never actually done anything "tough", so he uses his local Wednesday night beginners BJJ class as his own personal "proving ground". I've only run into a few over the years, but they're all D-bags.
Some examples from real life -
A guy so afraid to "lose" during a roll that he roids to the gills. He's not a fighter either. He literally only does BJJ and some sporadic weight training, but needs to be roided so that he can more easily beat up that 50 year old accountant ...
A guy who, if he got to class early, would put on the worst scream-metal you can imagine, pull the hood from his hoodie up over his head, look down at the floor and just pace until someone told him to knock it off. Like, come on man, WTF are you doing? We're not about to have the Thunderdome in here. Master Blaster isn't going to descend from the cielling on bunji cords and attack you with a chainsaw. Why are trying to pump yourself up so much? It's just a jiujitsu class and everyone in here is your freaking team mate so chill.
A girl joined a gym I trained at to help her deal with some anxiety issues. In particular, she wanted to deal with the discomfort she felt when people got too close to her. She's TINY. Probably 105 pounds with her gi on. At some point one night, the upper belts who were watching to make sure she ONLY rolled with upper belts who would work with her lost track of her partners. SHe ends up with the guy from the previous paragraph. He's in his mid 20's lifts every day. Proceeds to immediately smother her in side control and use excess pressure. Gets mad when I (one of the upper belts who sadly lost track) tells him to cool it. "How's she gonna learn bro!"
A guy who, as a one-stripe white belt thought he was the SH@T because he tapped a blue belt. I will give him that it WAS a legit tap. Not one of those times where he was just being allowed to work. It was just that it was a tap on someone whom he outweighed by literally almost 130 pounds. 6'3" college football player vs 5'4" (the only guy shorter than me in the whole gym) hobbyist. He got said tap by basically knocking the dude nearly unconcious with a power bomb. EVeryone's rolling and then all of a sudden there's a loud BOOM! This idiot then talked endlessly about how blue belts are nothing and maybe BJJ isn't for him because it's "Just so easy for me". Then decided everyone who refused to roll with him was "ducking". Yep.
I can handle just about everything else. Have no issues telling someone they need to shower/wash their gi/clip their nails etc. Can deal with someone rolling harder than I want and don't really care about that white belt trying to heel hook me in a gi. But if you're "that guy" who's trying to use a regular public BJJ class filled with non-athletes and people who just want to drop some weight as his own personal Agoge - you sir, can go right to hell.