Two words: Bang Stick.
It's a device used for offshore fishing. Instead of taking a shotgun out onto the water (dangerous for many reasons) you use this stick. It's about 2-3 feet long, and there is a metal piece on the end where you load a single shotgun shell. Pull the safety pin and slam it into the fish for instant death.
Instead of a boat it's in my house, instead of a fish it's a zombie's skull.