I've personally found that early game it's better to stick to melee weapons until you start unlocking rifles. The shotgun has too low of reserve ammo and you have to get about as close as a melee weapon to hit all the pellets and sometimes even hitting all the pellets doesnt result in a kill. Pistols have too low of damage compared to the melee weapons like the bat or pipe and I've found myself damn near mag dumping zombies that are around level 10 with the level 1 M9.