I've told this story on TalkBass before, but it's a good one.
Back in my high school days, the band I was in was playing a New Year's party. Just at a friend's house, 50-60 people, no big deal. But we were getting paid for the first time, so we were thrilled. Anyhow, we were playing on a rented PA. I was the only one who sang back-up. First chorus of the first song rolls around, and I step up to the mic...BLAMMO!!!
The rented PA had a grounding "issue". Me playing my bass grounded everything once I was close enough to the microphone. A little blue lightning bolt shot from the mic to my upper lip, knocked me backwards, and blew every fuse in the PA and the house. Luckily, I suffered no permanent damage, and one of our friends was studying to be an electrician. He fixed everything in the PA and replaced the fuses in 1/2 an hour. Once I shook the cobwebs clear, we kept playing.
But I did walk around with a little black burn mark on my lip for a couple of weeks!