When people think they're sooo good at something, saying they're better than other people, and they're just terrible themselves at it. I have this classmate, that thinks he's doing a perfect British English accent, during our English classes. I seriously cringe every time I hear it.
Also, when I'm chatting with someone online, and they only respond with "lol" or just a 2-3 word message, when I've written a longer message to them. It really makes me feel insignificant.
Also, when I'm chatting with someone online, and they just leave me hanging without saying "goodbye", "see you" or just a simple "brb". Am I not worthy of a small message telling me, you won't be able to respond for a while?