These bullets were crafted by hunters as an easier means to stop certain types of monsters. In 14.01 Stranger in a Strange Land, one of the Apocalypse World hunters showed an assortment of these specialized bullets to Mary.
Silver bullets coated with a tincture made from holy oil, sage, and myrrh, followed by the recitation of a spell to mimic the original etchings. When used with the Colt, these bullets are capable of killing (nearly) anything.
Hollow point bullets injected with holy oil. It is unknown the effect these bullets would have on an angel or demon.
Hollow point bullets injected with witch-killing brew. These bullets are capable of killing witches who are otherwise invulnerable to traditional methods of dispatch.