In at least one of my son's many zombie-battling video games -- it might have been one of the Evil Dead series -- you can shoot zombies all day with shotguns and handguns......and they keep coming at you, unless you manage to decapitate 'em or otherwise inflict massive damage. On the other hand, if you run out of ammo, you can kick them or slash at them with a knife. Apparently, grazing by a butter knife or being touched by leather cause immediate and sudden death.