PC's that pretend they're doing something, when they really dies like a dog half an hour ago.
Days that start out cold & teeming with rain, the change their minds and turn into heatwaves, just so that whatever I dress in, I'll either freeze or boil.
People who are clearly suffering from something both debilitating and highly infectious, but come in to work anyway. Then they do nothing useful, but sneeze all over everyone all day. Thanks for sharing!
Helpdesk callers who say "It just went funny all of a sudden" and expect you to know what's wrong, presumably by figuring out telepathically what they did to it that they're not telling you.