Hippopotomonstrosesquipedaliophobia

More commonly referred to as simply The Phobia, Hippopotomonstrosesquipedaliophobia is a revolver with an overall length of 20 inches and a total weight of 50 pounds. It is chambered for 13mm, armour-piercing, high-explosive incendiary rounds that are each composed from depleted uranium of all things.

It is equipped with a unique variant of the Water Dial that is capable of refueling itself with any of the water vapor in the air. Its firing mechanism is completely dependent upon the functionality of the aforementioned Water Dial, for its bullets are propelled by water that has been pressurized as condensely as physically possible.

Trivia

 * Hippopotomonstrosesquipedaliophobia is the fear of big words.