It has been 20+ years since it happened, but I'm pretty sure I was standing in a little puddle, or my hands were wet (can't remember which), and my wrench just happened to bump the positive terminal and it was like "POW! Right in the brain!". Thankfully I didn't latch on or anything. It was instantaneous, and over in half a second, but it rocked my world for that half second or whatever it was.