So far, so good with the machine stuff but since my field has been electronics, I've done a few dumb things in that field.
When I was in high school I built a portable "black light" using a small UV fluorescent tube powered by batteries. A fluorescent tube requires a fairly high voltage to generate its internal discharge so I taped together three 145V batteries in series. These were serious batteries-- surplus military backpack radio batteries that were each about 10" square by 3" thick. They had a flat connector, so to make the connections, I soldered wires to nails and inserted them in the battery sockets. Voila! the lamp came on and I fooled around with it, seeing what was fluorescent under black light. To shut off the lamp, I had not used a switch so I just reached over, grabbed a nail in each hand.... Yeowww--- the worst shock I've ever gotten! Totally dumb move.
Regards, Neil Tucson, AZ