Gee Haw Whammydiddle

See introduction at this link.
Cut a couple hardwood twigs about 8" to 10" long and about 3/8" to 1/2" in diameter. Whittle one down to about 1/4" in diameter back to about 4". Notch the other one with about eight notches over a length of 3" to 4".

Make a blade from light metal about 1" by 3/8" and drill a hole in the center. Put a nail, small enough to be loose in the hole, through the blade and drive it into the end of the stick with the notches. The blade needs to be free-turning, and pretty well-balanced. (The drawing may look like the nail is going through the edge of the blade. Not so; it goes through the flat side.)

As you rub the whittled stick over the one with the blade it creates a vibration from the washboard effect, making the blade turn. You can make it go "gee" or "haw" (right or left) depending on whether you touch it with your forefinger or not, because it changes the way the stick vibrates.

If you're a good Gee-Haw-er you can move your finger so nobody notices, pretending to control the direction of the blade by saying "Gee" or "Haw" to the sticks. My dad about drove me nuts trying to figure this out and I did it to my kids too.