bow and arrow. its silent so you wont alert other zombies in the area and you can reuse the arrows or a crossbow for the same reason. but I would carry a .22rifle because of the versatility and the availability of the ammo
during the zombie apocalypse you want to be as tactical as possible because zombies are attracted to noise. and you want to be able to reuse your ammo that's why a crossbow would be your best option. that's my answer and im sticking to it. and to the guy who would use a barrett good luck with that cause I forsee you giving up using it because of the overall weight of the weapon system and the ammo used.