Ban Hammer is a special weapon. It will insta-kill any non-boss enemy.
Obtained from any Treasure Bag with 1:150 chance, after beating Plantera.
Tip: It will insta-kill the Dungeon Guardian, making it very useful if you're lucky enough to get it before fighting the towers.
It may be considered cheating due to it killing hard enemies from mods such as the reaver shark, eidolon wyrm, dungeon guardian, if you get it then you may use it through your playthrough if you want.