I was demoing a robot and one of the power distribution block's wires came out. I didn't know where it was supposed to go (and no electronics subteam members around), so I tried plugging it into a different slot.
Sparks. Lots of them.
Luckily no harm was done whatsoever. I did learn that I probably wasn't a good fit for the electronics subteam.
Also to pay a bit more attention to safety. It's a good idea.