This is a sex move named after the titular B-Movie Action Hero. It starts off with you revving your hand like a chainsaw, slamming it up the vagina or ass (your choice) of your partner, yelling "THIS IS MY... BOOMSTICK!" then mimicking a shotgun blast by opening your hand inside the other person. At the end, pull out your hand, extend your chin, look down at the other person and say (in your most bad-ass of voices) "Groovy."
My girlfriend let me do the Bruce Campbell on her and i didn't even have to use the Necronomicon.