well this is going to sound pretty stupid, and it was
i was removing a battery in the rain (!) and managed to cross something, I still can't recall what I hit, but there was a pretty loud zap and huge flash and I got the crap shocked out of me. I crossed something with my left hand, and the 12mm wrench and two halves of a terminal brush in my right hand all got welded together. my right hand wasn't touching anything else.
luckily this didn't result in injury to anything but my pride