Answer:
I have a face, yet no senses. But I don't really care, because time is of the essence.
Goes over all the hills and hollows. Bites hard, but never swallows.
Useful tool for who in darkness dwell. Within you, corrupting like a deadly spell.
What is never used unless it's in a tight place?
What is the smallest bridge in the world?
I am rarely touched but often held. If you are smart you'll use me well. What am I?