Answer:
A thousand wheels but move I do not. Call me what I am call me a lot.
In wealth I abound; in water I stand; as a fencer I'm valued all over the land; at Venice I'm famous; by farmers I'm prized; respected by law yet huntsmen despised; consternation and ruin ensue when I break; And the beasts of the forest advantage won't take.
There is one in a minute two in a moment and none in a thousand years. What is it?
I jump when I walk and sit when I stand.
I hide in a dark tunnel awaiting my time. I can only be released by pulling back. Once released I may do unstoppable damage.
No matter how little or how much you use me, you change me every month.