Looks like there will be many comments / questions about the cannon.
It just an add-on like other FR Pokemons.
Because we kinda dislike the concept of original Rhyperior.
Rhydon is already awesome, so why its evolution, Rhyperior who should be called as "Rhydon Superior" getting fatter ? (looks like its because too many eating rocks
Can't imagine what will become the final evo of Rapidash, Arcanine, Ninetail , etc
So, in order to compete with others FR Pokemons, Rhyperior decide to super-diet and equip his secret Cannon.
His aim is one, to become the Pokemon's "Ultimate Weapon"
Pokedex no 464RHYPERIOR
Info taken directly from Pokemon.com official pokedex,and Serebii.net pokedex Rhyperior © Satoshi Tajiri, Ken Sugimori , and Nintendo
Image © FR Brothers