People who refuse to explain their actions and opinions at least once. People who are hateful, rude, angry or mean without good reason. This is a big one. People who believe their opinions are right while others' conflicting opinions are wrong. This is also a big one. People who consider simple facts concerning race, gender or otherwise to be racist, sexist or otherwise prejudiced. Parents who let their children get away with bad behavior. This infuriates me. I literally have to fully concentrate on staying as calm as possible when witnessing this. People who are overly apathetic and uncaring. People who forget everything that's said to them. It makes me wonder why I bother talking to them at all when they tell me they don't remember something I'd talked with them about several times before. People who hold a position of authority of some kind, but aren't fair or reasonable. This is a big one. I've gotten into some major arguments with a few of my not-so-great teachers while I was in school. Luckily, most of my teachers were quite reasonable, and I actually really enjoyed those teacher's classes and would often talk with them like I would friends.