a .22 Handgun, for longer ranges, something that runs on NATO rounds (probably the easiest to come across), and a good whacking tool. Me, my girlfriend and a couple friends (read: 5-6 man zombie party) have always made sure that we'd be ready come Z-day. Sort of as a joke, but we'd be more ready than others. You definitely do not need a large weapon, just something that will do the job quickly, efficiently and if need be, quietly.