-Hypocrisy-in just about any form. People who say one thing and do another, that sort of thing.
-People who call my office for help, and then insist that what I tell them is wrong and that it can't possibly be that way. If you don't want to hear my answer, don't call for help. If you're that smart, then why are you calling Tech Support in the first place?
-Complete and total pessimism-I can understand pessimism to a certain point, even I get that way sometimes. (though rarely...I'm one of the most optimistic, happy people you will ever meet). But at some point pessimism becomes a "woah is me" whining fest and half the time it's the person's own fault for the way they are feeling. Despite what some people think, the world is out to get them, and everyone's thought process DOES NOT include "and what can I do to hurt or upset
-Misuse of basic math terms. Always been a pet peeve. You DO NOT 'plus' something or 'minus' something, you 'add' or 'subtract' it. 'Plus' and 'minus' are reserved for use in reading things like 2+2 or 10-3. The misuse of the words to say "You plus 3 to 5" seriously grates on my nerves and makes the speaker sound like an uneducated idiot. (I apologize if anyone does it, it's just a real pet peeve of mine)
I'm sure there are lots of other things, but those are some of the top ones that come to mind immediately.