I was playing around with an old computer PSU (from the early '90s) and I accidentally forgot to pull the plug out when I flipped the "off" switch. As I was working with it, my (luckily rubber-handled) pliers contacted the metal components connected directly to the AC input, completing the circuit and causing a short which popped the circuit breaker to the upstairs electrical system in my house, completely blacking out the environment in which I had to unplug the power cord, navigate the insanely cluttered floor of my room to the door, and make my way downstairs to reset the breaker. Ever stepped on a lego in the dark? Try stepping on a PCB.