Pretty early on (16 years old, first week in college shop) I managed to get two fingers between a sanding disc and the table (adjusted too far out), trying to sand the edge of a thin piece of ply - That *smarted*. I've been super careful ever since.
Didn't stop a colleague dropping a mill table on my fingers though - still doesn't straighten
One thing happening that didn't occur to me, not machine-related, was out shooting with a fellow radio ham who had an Icom handy with him, just to monitor the local 2M repeater and catch someone he needed to talk to.
We were happily banging away at clays when his radio faded, so he swapped batteries and dropped the "flat" one in his trouser pocket - right on top of a 12-bore magnum cartridge...
Can you guess what came next?
The brass base must have made contact with the NiCad terminals, and even flat they can dump well upwards of 30A into a short for a few seconds - enough to touch off a shotgun primer!
After the smoke cleared and he stopped cursing we put some clean cloth over the gouge in his thigh and got off to hospital, luckily the round wasn't pointed a little higher, as his subsequent kid is a nice little chap
Dave H. (the other one)