Friend who's a professional carpenter and roofer nailed his hand to the roof one day. The guy's a safety nut, and never makes mistakes like that. But then he did. Power equipment plus advancing age will get us.
OK I can top this! ;-)
When adding an addition to our house that included a cold roof that first required a deck under the metal roofing, my wife offered to help up on the roof. Now the roof slope is pretty mild, and I was thrilled with the SPUNK shown by my rather timid better half (might be 3/4) . I held the ladder and steadied her steps as she got on the roof deck. We were putting down 1 inch boards onto 2x4 sleepers. She had hammer in hand, and nails in a bucket. With brief instructions given her on the nailing schedule, was pounding away about 10 feet down slope (fall protection).
Well, all the sudden my wife let out a mournful yelp and clutched one hand in the other, dropping her hammer. I lifted up, and took the three strides to her side where I saw drops of blood dripping from her clutched hands. "I'm a trained med first responder, so she trusted me when I asked to assess the injury. Somehow, And I can't imagine how, she had driven a 10 penny nail through the web of skin between thumb and palm. OMG! Needless to say, she does not "do blood" and went vasolvagle on me, and I had to shoulder her down the ladder and off the roof. Good thing there is not so much heft to her.
That was all 30 years ago, I remember, but NEVER bring it up.
I still don't know how a person can drive a nail through the hand that is supposed to be holding the nail. My guess is she "flinched" let go of the nail, and when the hammer fell a glancing blow and the nail bounced with enough energy to penetrate the nearby flesh.
Be careful, danger lurks!