Only a couple I an think of offhand.
An old spoke, cut in half. End is wrapped in electrical tape for grip. Used to get nipples into deep section rims or rims with without eyelets.
The second is a Bendix locknut remover made from two small steel pipe lengths and an elbow connector. One end has two notches cut out to engage the lockring (it's like a small version of a freewheel).
Oh yeah, and I often use the "hander"- my hand as a hammer when I'm too lazy to get my rubber mallet. But not sure if that counts.
Sean Flores
San Francisco, CA