[Undertoad]

Hey Mythbusters did that one early on:

The bullet did work as a replacement fuse, however when a short circuit was created, the wiring burnt up and the bullet did not fire. When the wiring was upgraded to a higher gauge, the bullet did fire out of the fusebox, but not with enough velocity to cause any serious injury. Though both Adam and Jamie admitted that the myth was plausible from their tests, they had to call it busted due to a lack of conclusive evidence...