Minecraft wiki entry for Snow_golems, associated text: The sheer number of snowballs will push mobs away faster than they can reach the golems. This usually occurs until the mob is either killed by the player, burns in sunlight, or despawns. This makes them very effective against zombies, and fairly effective against spiders if you have enough golems. They are fairly straightforward and open-ended to build, all they require is a place for several golems to shoot from. If they are in your wall of your house, you can remove a block behind them to break the snow from under them from inside your house, thus doubling as a snow farm and saving space.