Minecraft wiki entry for Combat, associated text: Dispensers can be loaded with a wide variety of ammunition, such as arrows, fire charges, snowballs, eggs and potions and will fire said items when activated by redstone. Loading a dispenser with arrows or fire charges and linking it to a (fast-cycling) redstone clock can turn it into a full-auto machine gun turret with enough firepower to level just about any mob that happens to be in front of it.