The water gun is a popular kids toy typically used for the summer season durring hot days. Water guns usually work best with water (not salt water though) as juice and other drinks can break the water gun. You put water into a part of the water gun and then fire the water by pumping it. Some water guns are more powerful than others and some can spray water in different directions. Super Soaker is currently number 1 in the water gun business, usually selling massive guns that can hold up to a gallon of water and spray hard enough to hurt other people.
In video games, water guns are usually used as weapons.
Water Guns in Video Games
A water gun is used as a weapon in most games. In Dead Rising 2, the water gun is a joke weapon. You can spray zombies with it but it will barely slow them down and is pretty ineffective. But if you combine the water gun with another object in the game world, you can turn your useless water gun into a powerful flamethrower.
In Super Mario Sunshine, Mario spends most of the game with a water gun strapped to his back, F.L.U.D.D. Not only does this water gun spray large amounts of water (it can be refilled by swimming in water) but it can also be used as a jet pack and also talks.