About 10 years ago, I put my then current knitting project down the side of the cushion on the sofa while I went to make a cup of tea. When I returned to the sofa I put my tea on the side table and plonked myself back down on the sofa.
Unfortunately, I sat on a knitting needle which went in my buttock near my back jeans pocket and came out near my front jeans pocket. It went straight through 
It didn't hurt straight away.
I managed to get up and (I don't know why) went to the downstairs loo and pulled the knitting needle out (steel 4mm needle). It was agony - hurt 100 times more coming out. It dragged my skin and it was really tough to pull out.
I told my husband that I was going to nip to minor injuries - he said that I was as white as a sheet. He drove me there: I was sat on folded towels in the car.
I was fine - got a bit of iodine on each wound and small dressings. That was it. It just hurt when I walked for a couple of weeks.
I've never put knitting needles, pointing upwards, down the sides of sofas since then.
But thinking about it, I've been using exact same needles today whilst knitting some baby items for my daughter's friend.
More than 30 years ago I was dressing my two year old son on my bed. I was rushing because he had to be at playgroup for a certain time. I finished dressing him and asked him to jump up.
He did as he was told and bounced on the bed when he jumped up. His massive head hit me just in the right spot under my chin and the force lifted my feet off the floor and I was thrown backwards.
Spent the rest of the day in hospital with my newborn daughter (who I was breastfeeding) with a broken jaw which ended up needing a couple of procedures to fix. Totally my fault for rushing, and instructing my son to 'jump'.