Answer:
I start new then become old. Start clean but become dirty. I usually start big then become little. What am I?
In your fire you hear me scream creaking and whining yet I am dead before you lay me in your hearth.
In a tunnel of darkness lies a beast or iron. It can only attack when pulled back. What is it?
Used left or right I get to travel over cobblestone or gravel. Used up I vie for sweet success used down I cause men great duress.
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.
What gift should you give blind people, drunks, and nerds for Christmas?