I work in tech support, so I have a number of pet peeves.
I'll limit them to the most frustrating.
People who call you for a problem, you tell them you'll be right there and so they leave.
Me: "Where did so & so go?"
Secretary: "Oh, she went to lunch. Did you need her?"
Me: "No, I know everyone's password, so I'll pull it up from memory and log in."
Another big peeve is people who send you generic work orders with no useful information at all.
User:When I double-click the icon for that program I use all of the time, it gives me an error. Can you fix it?
Me: smashing head on table
I could really go on for days....