I can't stand it when people can't talk without invading your personal space.
A guy on my staff - who seems to be the source of most of my work frustrations - is guilty as hell of this. He also happens to have the worst breath imaginable. I think he has tonsil stones, because there's nothing else that could possibly produce the rovolting, rancid breath that this bastard has.
When I stop by his cube to talk to him, he'll immediately get out of his chair and move to within 6" of my face while he listens to what I'm saying. WTF is the purpose of that? Can you not hear me when you're sitting in your chair 2 feet away?
I really can't stand that guy...