Hmm, couple of times here. I really hated it when i had to have teeth removed, they bled like crazy and my mouth was sore for weeks after it, and also when i got my brace on and it absolutely KILLED for the first week.

Another time was when i was 6, and i was running on the patio and then fell... onto the lawnmower blade which was propped up against the wall and gashed my knee open right across the leg. It didn't hurt at first, because i actually sat there for a couple of seconds and watched the blood ooze out, but then my mum came around the corner and quickly whisked me off to be bandaged up.
Also, when my brother jumped on my little finger and broke it, YOWCH i can feel the pain now!!!!

But i think the worst pain of all is emotional pain, especially when you lose a dear pet