Q from Star Trek: Next Generation - Because of course you have the power of a god and what do you do with it, you chase the Enterprise around the galaxy catch it and then DON'T feed Wesley Crusher to the Ravenous Bugblatter Beast of Traal.
All right, since it's been a few hours, I'll claim Z. Zealots, the extreme ones. Annoying aspects of computers, hardware or software. Automatic update popups.
Driver Updates, and never finding the right one (Seems to me Elton and Carrie where having a nice little back and forth towards the end of that last list =P)