Anyone have a good idea for a homemade instrument?

My son is working on a project for elementary school. He is to make a homemade instrument. He has to e able to demonstrate it to the class, and explain how the instrument makes sound, vibrations, pitch, and volume. They give a few suggestions, but I really would like for him to be able to make something different than what was given for examples. The idea's that were given were as follows:

Bass Fiddle w/coffee can/string %26amp; a wood block

Rubber band, Shoe Box Guitar: Shoe box, rubber bands

Tin Can Drum, Glass Bottle, Xylophone - w/copper tubing %26amp; tape, Clay Flower pot

Bongo Drums - w/Oatmeal boxes %26amp; tape

Pie Tin Cymbal

Plastic Egg

Spoons

Straw Flute %26amp; Trumpet

Comb Kazoo

Glass Bottle Horn

I was thinking about making a rain stick w/a paper towel tube w/placing frozen orange juice tops half way through either side of the tube - sticking out somewhat through the sides, and attaching them w/tape then filling the tube w/macaroni or rice for the sound %26amp; having him decorate it.

Anyone have a good idea for a homemade instrument?
i would go for the rain stick! we have a really one and the kids love it!
Reply:any kind of percussive instrument would be easy...look at the Pringles commercials.