I've had two memorable (to me, at least) X-acto encounters. When I was about eight years old I sliced off about at third of a thumbnail and a considerable amount of the flesh below it - not enough to send me to the emergency room, but pretty awful from the standpoint of an eight-year-old. I asked me father to come play his violin for me, just to remind me that there was something in the world that was worse than the way my thumb felt. (He did - and it was.)
Quite a few years later I got into the bad habit, whenever I felt (but didn't see) an object fall off the workbench in front of me, of snapping my legs together in order to catch it. One night I felt something roll off, snapped my legs together, and immediately felt one leg go numb from the thigh down. When I looked downward I discovered an X-acto knife with its #11 blade buried in my thigh. It didn't actually bleed much, but it was an interesting feeling.
Then there was the time I was learning how to use my brand-new Unimat SL lathe. (This must have been in about 1975.) It came with a three-jaw chuck; anybody who's used one knows that it consists of several rather sharp-edged pieces of steel that spin around. Spin around so fast that you can't see them. I was practicing turning a small piece of wood, leaning down over the lathe with my nose about eight inches from it. I was carefully sliding the turning chisel (held with both hands, in the prescribed manner) along the length of the dowel, and just casually slid it into the chuck. The chisel, at a speed of at least 90 mph, flew up and hit me in the teeth. The next day I went to the local dealer and bought a Unimat Jacobs chuck - which is basically smooth in configuration and relatively harmless. That three-jaw chuck, which is now about thirty years old, still scares me.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.