People who, when on their computer using a keyboard, still type like they are texting. I can forgive someone for typing like an idiot when texting but when on a computer and they still use "u" "r" etc, it drives me insane. I often voice my opinion on it. It makes me laugh when they try to insult someone like that. It takes more time trying to figure out what they said than the time spent for you to get insulted by it.