Answer:
I am the tool, for inspiring many. Buy me in the store, for not much more than a penny. Don't overuse me, or my usefulness will go.
Look into my face and I'm everybody. Scratch my back and I'm nobody.
Weight in my belly, Trees on my back, I travel fast in my place, but feet is a feature I lack
What goes up when the rain comes down?
I grow where no flower grows, where no light touches the walls, up or down, that I don't care, was here before people were.
What covers its face with its hands, speaks no language, yet most known what it's saying?