Ouch, those are brutal! Especially the nail in the head!
1. As sleeper (basketball cafe) and I discussed, I tore my ACL in college playing basketball. The tear was loud, another guy and I heard it rip. It hurt, but wasn't awful.
2. I tore my cartilage in my other knee during high school. It ended my senior year baseball season
3. My cousins and I (when we were about 10) were hitting golf balls and I accidently walked in front of one cousin and got smacked square in the nose with a golf ball. My folks were pretty scared about that one, but I just needed ice.
4. And nothing like giving your thumb a good crunch when toenailing some 2x4's. I've given myself a good dizzy a few times with that!