Answer:
Look into my face and I'm everybody. Scratch my back and I'm nobody.
Autumn leaves and bad bowlers wreak havoc on this
It can cause deflation of tires when dropped from the rear of spy cars.
Break it and it is better, immediately set and harder to break again
Halo of water, tongue of wood. Skin of stone, long I've stood. My fingers short reach to the sky. Inside my heart men live and die.
I am rarely touched but often held. If you are smart you'll use me well. What am I?