Let's see, there are a couple of bad memories:
-when I was 12 I had an infected big toe that required minor surgery. The doctor had to inject the anesthesia right into the infected part. It was awful for a second there.
-I had played a particularly grueling one day tennis tournament, probably around 14 or 15 years old. I woke screaming in pain that someone had stabbed me in the legs. Now had I been fully awake I'd have realized it was just bad cramps, but waking up to that pain made it terrifying. I remember my mother rushing in, deducing the problem with my contorted legs, and straightening them. God, moms are awesome sometimes.
-I was playing a spirited game of football with my family on thanksgiving a few years back. Long story short, my brother dove and reached around me to strip me of the ball. He missed the ball but latched onto my shorts. He pulled my down to the ground via my testes. It was difficult to move for a few days. Probably the worst lingering pain I've ever felt.
-Racquetball. The last time I ever played. You're obviously supposed to wear glasses and a cup for racquetball, but I never did. I especially hated the glasses. So I served the ball, and when you serve in racquetball the ball ends up going behind you to the returner. I always "cheat" by turning around to see which direction the return is coming. I turned around and 150mph return hit me flush in my junk. I hit the floor and was there for probably 5-10 minutes. It left a burn mark on the head of my penis. That was the worst of it. The pain subsided substantially by the time I went to bed that night.