If you were to ask my current boss what drives her crazy, it would definitely be people scheduling shifts and then not showing up or promising that they're going to make it to a shift and then not showing up to said shift. It is something that she has quite openly talked about her distaste for on numerous occasions, that and employees who don't take the time to learn the job and after two months of working there, have the proficiency of an employee who just started that same day. Those two things would definitely be the two that drive her the craziest, I would say.