Rainglock has the highest base Special Attack stat of all Water-type Pokémon.
Rainglock was the original proposed Water-type starter for Pokémon Clover. Its base form would have been a simple raindrop, with its second evolution gaining a gun and its final gaining a bunch of dead black people.
Rainglock holds the record for the time between design creation and actual inclusion in the Pokedex. It was created in 2014 but was not added into the dex until 2017, a few months before the release of the 8-Gym Demo.
On April Fools' Day 2019, Rainglock was given a fake alternate form that gave the glock a bright orange tip, turning it into a toy gun.
It has nothing to do with the pokemon gun joke
Are you sure? I mean, its literally a raindrop with a gun
It's a raindrop with a fucking gun.
Rainglock's shiny form is likely meant to represent urine, due to its yellow coloration, and the gun turning gold could be a reference to Goldeneye's Golden Gun.