This is kind of a lame one but it's something my boss always does that annoys the fuck out of me.
I have a 9-5 desk job, and my boss is usually very reasonable. Except that EVERY. SINGLE. ONE. of my daily tasks (enough tasks to take up an 8 hour workday) have to be done “first thing in the morning”. It's literally impossible. I know that, and he knows that too. But he just needs to be sour about something so he says “well that should have been done first thing when you got here” every morning, after I completed yesterdays thing that should have been done “first thing in the morning”.