Hmm I remember a certain Sphinx object in Heroes of Might and Magic 3, it had TONS and TONS of riddles, better post a few:
"When one does not know what it is,
then it is something;
but when one knows what it is,
then it is nothing.
What is it?"
"What is neither inside the house,
nor outside the house,
but lets you see both?"
"There was a green round house.
Inside the green round house was a smaller white house.
In the white house was a red house.
And living in the red house were lots of little black babies."
Should be enough to start myself off for now