I have an eccentric grandfather. For my birthday one year he gave me a micrometer, a device used to measure things between zero and 25mm. I was thirteen. He gave it to me in a wooden, felt lined box and said:

"You can use it to measure the thickness of paper!"

Thanks grandpa.

EDIT: For those of you saying that this is a great gift for a 13 year old, here is a list of phrases you will never hear:

1. Hey can I borrow your micrometer?

2. This man is dying! Quick someone get a micrometer!

3. I'm 13 years old and I need to measure something between 0 and 25 mm! Where's my trusty micrometer?