I've had a pretty mundane guy life. Broken bones, head injuries, torn ligaments, thumb slammed in car door, fireworks mishap, stab wound, frozen paintball shots, stepped on legos, etc. But the worst for me was food poisoning. Man, that hurt like hell. Yes, that's my vote. I just remember being rolled up in a ball of pain, praying, wishing I were dead. Not a very impressive story, though.
I'm sure the CB collective has experienced things far more painful than me. Give us your best shot.