I have three.
1) Was when i was a baby and is a burn mark. Mum was checking the temprature of my milk and accidently dropped the warm milk on my foot, i now have a coin sized circle of what looks like radiation spots on my foot.
2. Was when i was 'bout 5 or 6. Was in the bath with my brother when we started fighting, previously we had been playing with a glass vase and forgot all about it, he kicked me and i moved my elbow back to stop me from from falling and elbowed the glass vase. I only felt the pain when i saw the blood literally pouring from my elbow. Got butterfly stiches.
3. Was when i was about 14. Was biking home from school when a car pulled in front of me. I hit the area where the front left wheel is and flipped onto the bonnet(i remember looking through the windscreen and into the horrified faces of three chicks) i dont remember much but later realised i was bleeding from an inch sized cut in my leg, i dont know how it got there, i didnt require stiches but its still there as a reminder.
Funny thing is the other people blamed me for the accident when i had the right of way.