Vibraslap
Noun: A percussion instrument consisting of a piece of stiff wire bent into a U-shape connecting a wood ball to a hollow box of wood with metal “teeth” inside. The player holds the instrument by the bend piece of wire and strikes the wood ball, which hits the wooden box of teeth, creating a sound not unlike that of a rattlesnake's tail. It was invented by Martin Cohen and is a modern development from the African rattling jawbone instrument.
You can hear the vibraslap in lots of 70s music, particularly in film score.