My worst ever manager was at my first job. He was a dumb, conceited asshole who somehow made everyone believe he was the best at what he did. Luckily he took special interest in me (me being a young girl in my early 20's and all), and tried to spend as much time with me as possible, to the point where he got jealous when i preferred to hang out with another coworker rather than him on business trips, or took smoke breaks with someone other than him.

To name just one example, we were drinking at my coworker's hotel room until late, at which point I fell asleep on his bed. I was later told that my manager wouldn't leave and let the other guy sleep (assuming that there was something going he did not give his blessing to). Finally he left at about 4 am, just to appear the next morning ten minutes early to pick us up, directly at my hotel room of course, to check on me. He was the sneakiest, slimiest bastard I have ever met.

Of course I left the company as soon as I could, and told HR about it. Don't worry though - by the time I left he's found himself a new 19 year old intern to harass, who happened to enjoy the extra attention.