Machine guns are your second choice because they have a rapid fire rate and have lots of ammo. Sub-machine guns are best because they are more accurate than machine guns, waste less ammo, and are more lightweight (in most cases). Shotguns are powerful but theyre arent accurate and are only good at close range. Not to mention they cant hold very many shells. Sniper rifles suck because they can only take out one or two zombies at a time and you usually need to be at a distance.