I worked with someone that could tell if a car needed wires/cap/rotor by putting his fingers in the end of the wires and cranking the engine. I also saw him pull one of his own teeth out, in the shop with a pair of pliers, because it was hurting
Used to shoot with a former SF type working for Blackwater. Saw a scar on his forearm and asked what happened. "Got a tattoo when I was drunk and didn't like it, so I burned it off." Said he used a propane torch to heat a spoon. At first, I didn't believe him, but as I learned more about him I have no doubt.