What Am I Riddles

Question: I have all of your knowledge but could fit in your hands.

What am I?

Question: I join you in battle, fist clenched tight.
We pound three times with all our might.
If my rival decides he will sign for peace;
I'll crush him, and the fight will cease.
But if he lays his hand down flat;
I'll suffer defeat, that is that.

What am I?

Question: I build bridges of silver and crowns of gold.Who am I?

Question: I am your most powerful weapon; I come before your eyes.. I help you seek the truth, yet I often give you lies. What am I?

Question: Stars, scores and springs have them. Fingers, and backs have them. Keys, switches and cups have them. Leaders and mothers have them.