A lot of very interesting anecdotes here, but precious few are of our own idiocy. I will attempt to remedy this. A decade-and-half ago i was working in the deli department at my local supermarket, it was peak hours, lots of customers, and i was slicing some italian cured meats for a customer, in thin slices. I was using one of those machines with a large circular blade that rotates, and a dial you set the thickness with.
Another customer asks a question and i'm instantly distracted, look up, but forget to tell my arm and upper body to stop slicing, so it does another push as it had been doing for the last few minutes.
What happens next is truly remarkable, and i remember it very vividly. As i push the part of the machine that moves forward and slice i pause and look down. That didnt feel quite right.
At this point there was absolutely no pain, no blood, but as i remove my hand i see that the edge of my thumb is missing part of the glove, and as cool air hits my freshly severed nerves there is this strange feeling, a little discomforting, but above all weird. A few droplets of blood emerge. I slap on another glove, try to locate the tiny bit of thumb that's missing, the show must go on, customers waiting.
Thankfully i do and it fell nowhere near the cured ham i had sliced so all was good, packaged it up and handed the customer the package. The wound healed remarkably well, but then again we kept a clean shop(minus the body parts).
That thumb is still to this day ever so slightly flatter in its curvature compared to my left, unsliced thumb. A nice reminder to never let yourself be distracted when near something that can hurt you.
I'm just thankful i was cutting as thinly as i could, we often cut roast beef much thicker...