When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

What can you hold in your right hand, but never in your left hand?

The picture shows the dice results in each couple of throws. If they are actually following a pattern, can you find out the missing one?

Count the number of lines in the image below ?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

A boy and his father are caught in a traffic accident, and the father dies. Immediately the boy is rushed to a hospital, suffering from injuries. But the attending surgeon at the hospital, upon seeing the boy, says 'I cannot operate. This boy is my son.' How is this situation explained?

How can you make number one disappear by adding something to it?

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?

A little girl goes to the store and buys one dozen eggs. As she is going home, all but three break. How many eggs are left unbroken?