The Qwack-O-Ray can be upgraded to the Qwack-O-Blitzer with use. In challenge mode, it can be upgraded to the Mega Qwack-O-Blitzer.
While the Qwack-O-Ray does not appear in multiplayer, the Morph-o-Ray can morph enemies into ducks.
Before Up Your Arsenal
Prior to the Qwack-O-Ray, the similar Morph-o-Ray which transformed enemies into chickens, and Sheepinator which transformed enemies into sheep, had been used. Neither of these weapons could be purchased from a vendor, however.
Up Your Arsenal
The Qwack-O-Ray could be obtained upon reaching Aridia for 200,000 bolts from any vendor. It could then be upgraded to the Qwack-O-Blitzer with use, which can upgrade to the Mega Qwack-O-Blitzer for 300,000 bolts in challenge mode.
The Qwack-O-Ray is a light blue and grey pistol, when at later upgrades becomes orange instead. The Qwack-O-Blitzer is a larger carbine with a left-hand grip, many glowing blue canisters and a larger nozzle. The ducks it morphs enemies into are standard ducks at first, though the deadlier ducks become darker orange in color.
The Qwack-O-Ray fills up a bar in the UI which, once full, transforms the enemy into a duck. It fills faster the weaker the enemy is. While initially very niche, is surprisingly useful once fully upgraded. At V2, the ducks lay explosive eggs, which automatically seek out enemies at V3. At V4, the ducks will attack enemies, and at V5, they create a phoenix that follows you and charges into enemies, deal explosive damage. This makes it most useful at morphing smaller enemies to then attack the larger enemies.
Alas, it takes time for it to reach its most useful version, the Qwack-O-Blitzer, which does not directly address its main shortcomings. For one, the weapon cannot be used while jumping or crouching and must be fired at an enemy without being interrupted (such as by taking damage). It works best on the smallest and weakest of enemies, and only at close to short range at that. Due to the way it works, its upgrades added potential, and the requirement of large amounts of weak enemies to be most effective, it is by far the best weapon to use in the Aquatos Sewers.