How about a Heavy bow that shoots mini Valkyries, that upon precision kills spawns SIVA nanites [spoiler]I'd call it The Tyrant's Wrath, and let is randomly drop from a Heroic 7th wave EP (Heroic EPs would require a consumable you get from Ana that you enter into the EP node and then it make the EP wave the same light level as your Guardian, and drops Warmind Grade Mods, EP set Armor with perks, and some new IKELOS Weapons...)[/spoiler]