Not so much a "hate" thing, but definitely a massive pet peeve. If I set up an appointment with someone for a certain time, I expect them to be relatively on time. Meaning, a couple minutes late to the appointment is no big deal. However, it is NOT ok to make someone wait 20 minutes without a peep out of them. To make things more irritable, someone who hasn't set up an appointment gets to see an advisor while I sit and wait?? Not cool, at all.