Water Gun

Water Gun is Squirtle's Neutral B attack. It is functionally similar to Mario's F.L.U.D.D. in that it utilizes water, requires a charge, does no damage, and has only knockback, although it charges faster than F.L.U.D.D. If you start charging the move in the air, Squirtle is able to move left or right while charging. When used uncharged, it does a short ranged attack that deals about 12% damage with minimal knockback. The unique properties of the charged version mean that with practice, they make a good, but hard to use and learn, edgeguarding move.

You may also change the full spray's direction by tilting up or down. When fully charged, Squirtle can hold the charge and battle normally until the player presses the Special button again.

Techniques
A fully charged Water Gun can be performed on an opponent who is in his/her helpless animation trying to grab the ledge (this can also work with Mr Game and Watch, Sonic and Peach after they have used there third jumps). Doing so will push them away from the ledge and fall to there doom. You can also use Water Gun on an opponent that is swinging a Hammer. Since players cannot use midair jumps and up specials, they would most likely be KO'ed. All of these techniques can be used by Mario's F.L.U.D.D.

This and FLUDD are particularly useful against Ness and Lucas because it pushes them away from PK Thunder.

Origin
In the Pokémon universe, Water Gun is a common attack for most Water type Pokémon, Squirtle included. As it is learned at an early level, it is rather weak (since it has an attack strength of 40) and often replaced by stronger attacks, most prominently Surf and Hydro Pump, because of their higher damage output, as well as HM03's infinite usage. It also appears in Anime, as an incredibly common move for water types on the show.