I hate:
People that have everything they own monogramed.
People who give nasty criticism and call it "feedback"
People who start sentences with "Don't take this personally but..." and proceed to say things you can't help but take personally
People who CC your boss on emails unnecessarily
People who hit "Reply All"
People who stand at your cubicle while you're on the phone, sighing, pacing, rolling their eyes and then when you say, "Can I help you" they say "Oh, I'll just wait until you're off the phone"
People who when you get off the phone for their very important question, get distracted trying to to read what is on your computer
People who you catch reading the notes on your desk when you come back from the bathroom and go "Oh, hey, I was looking for you!"
People who won't look you in the eye when they talk to you