Fell on the head of a nail when I was young and tripped up the stairs (weighed down by my large head, I'm sure), I didn't even realize it until I went to get up and realized I was a little stuck. I panicked, stood up and a piece of my skin covering my left shin was still attached to the nail...on the stairs.
Straight to the bone.
When I was little (again, I'm sure the weight of my head is the culprit) I was playing on a scooter going down my next door neighbor's driveway, I fell about 1/2 of the way and skidded on my knees the rest, carried by the momentum. I stood up, thought ow, that hurt. Then I yelled for my dad and he stood there in horror. Turns out the skin on both of my knee caps was gone.