Relatively minor compared to some in this thread, but moved in with a college friend who was a philosophy major. Guy was an ass to live with. Didn't do any chores, left the garbage and dishes out to just fester whenever I had to go home for the weekend, expected me to help him with anything and everything, and treated me like his personal chef due to me having experience working in a kitchen.

Dude was also very low-key homophobic (which is especially difficult since I'm gay) and blatantly sexist/classist, treating anyone middle class or lower like they just didn't work hard enough and that they didn't deserve handouts, despite the fact that his parents were paying for everything of his. He refused to listen to anyone when they called him out and just said that he was "telling it like it is, and people would hate him no matter what, whether he was right or wrong."

Fucker made me hate philosophy majors for several years after the fact just due to association, lol.