Answer:
A mile from end to end, yet as close to as a friend. A precious commodity, freely given. Seen on the dead and on the living. Found on the rich, poor, short and tall, but shared among children most of all.
There are millions of me. I am very small but when moving fast I am deadly.
There are two meanings to me. With one I may need to be broken, with the other I hold on. My favorite characteristic is my charming dimple.
It's anything but amusing when this body part gets hit.
Flat as a leaf, round as a ring. Has two eyes, can't see a thing.
What sphinxes employ and players enjoy.