Best riddles

I am a fruit. Remove my first letter, it's a crime. Remove my first and last letter, it's a kind of music. What do you think am I?

What do you call a towel that has fallen in the sea?

I build up castles. I tear down mountains. I make some men blind, I help others to see. What am I?

You will throw me away when you want to use me. You will take me in when you don’t want to use me. What am I?

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

What do you throw out when you want to use it, but take in when you don't want to use it?

I can swim or walk for miles. I’m big with thick, white hair. I live up in the Arctic. What I am?

I heard of an invading, vanquishing army sweeping across the land, liquid-quick; conquering everything, quelling resistance. With it came darkness, dimming the light. Humans hid in their houses, while outside spears pierced, shattering stones walls. Uncountable soldiers smashed into the ground, but each elicited life as he died. When the army had vanished, advancing northward, the land was gree and growing, refresh.

A horse travels a certain distance each day. Strangely enough, two of its legs travel 30 miles each day and the other two legs travel nearly 31 miles. It would seem that two of the horse's legs must be one mile ahead of the other two legs, but of course this can't be true. Since the horse is normal, how is this situation possible?

It is impossible to keep it until you give it someone else. What is that?