Cap gun, roll caps ~ not only did we use them in the toy cap guns but we would take a hard surface like a rock or sidewalk and then hit each cap with a rock to make them pop and smoke. I remember the smell!
I'm pretty sure you can't buy anything even close to a realistic toy gun anymore. We played Cops and Robbers and Cowboys and Indians in the woods and didn't grow up to be bad people. Love the smell of those spent caps!