Jar of Fly Honey
As it's name implies, the item is a jar filled with fly honey. There is no sprite for it, but it is found in a garbage can inside a tent in Threed. After you are able to fight against Master Belch, using the jar will weaken him, allowing his infinite HP to finally be depleted. After the battle, it's use ends. He will take the item, and there is no way to get another one.