Kidney stones. I've had the tips of two fingers on my left hand chopped off, and even that didn't come close to the feeling of a kidney stone rattling down the pipework.
I have Medullary sponge kidney, which in short makes my kidneys a stone factory. It's a love/hate relationship at this point. On the plus side, I've found drinking at least 2 liters of lemonade every day has done wonders to stop my kidneys from feeling like they're trying to kill me all the time.
Reminds me of a person in Woodwork class who partially cut into their finger with the table saw
I also forgot one day to let the table saw get to full speed and was lucky I didn't get wood launched at me because the teacher noticed and stopped me from using the saw
I absolutely hated myself for forgetting that basic step because I had used the table saw perfectly fine before
By sticking them where they didn't belong... kind of hard to explain but I was working on a friend's lawn mower and lost my balance, I tried to push against the mower to hold myself up but my hand slipped, kind of bounced off the ground and the mower blade managed to catch them.
It didn't really hurt but I was more mad at myself for it happening. I brought the fingertips to the hospital but they were kinda smooshed, and they had to take a bit more bone out of my fingers so that they'd have enough skin to close it up.
Oh ya, it's fine.... It took a while to get used to having slightly shorter fingers, and it feels weird as hell when you bump things with them without the normal fingertip padding (Now it's just skin and bone hitting things) but I'm used to it.