Best riddles with simple answers

Pronounced as one letter, And written with three, Two letters there are, And two only in me. I’m double, I’m single, I’m black blue and gray, I’m read from both ends, And the same either way.

If I have it, I don't share it. If I share it, I don't have it. What is it?

One winter day, there was a man standing in the middle of someone's front yard. The person stayed there for several weeks without moving and the owner of the yard didn't mind. Eventually the man left. Who was the man?

I am only useful when I am full, yet I am always full of holes. What am I?

I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?

Farmer Brown came to town with some watermelons. He sold half of them plus half a melon and found that he had one whole melon left. How many melons did he take to town?

There is bomb on top of a computer; around the computer are a hairbrush, keys, phone and a cup. When the explosion comes, what item destroyed first?

Imagine you are in a sinking rowboat surrounded by sharks. How would you survive?

If you had three apples and four oranges in one hand and four apples and three oranges in the other hand, what would you have?

What's the best thing to put into a Christmas cake?