Screwing up at work

This thread was partly inspired by KCJ506's thread found here, although it doesn't have anything to do with customers. I was just wondering what is the worst thing you've ever done while on the job? Were you fired because of it? Did you opt not to tell your supervisor?

Well, I've been working at a warehouse doing sweaty Mexican labor for a few months, and I had to learn how to drive a fork lift. I was still getting used to the controls, and one day, I dropped some sheets off the clipboard attached in the forklift. I tried catching them instinctively, and crashed the forklift into the aisle wall. I was lucky no one was around. >_> I told my supervisor, and they were able to work out the dinks left in the metal rack. Even still, that was a pretty scary experience.

Gimme your best shot.

Jam it back in, in the dark.