Pokémon: Rotom-Wash
Wash Rotom was a Rotom that had entered a washing machine powered by a special motor, and it released water to intimidate opponents. It loved using water for pranks and would flood rooms-a troublesome troublemaker that splashed cold water around to cause mischief.
Ability: Levitate
Rotom-Wash had been the undisputed leader of the Rotom family ever since their types were differentiated in Generation V (Rotom-Heat saw more use in Generation IV).
The reasons for its popularity were mentioned above in the Rotom-Heat section: excellent resistances, only one weakness in Grass, and the same ability to check Flying, Fire, and Ground. More importantly, Water attacks, Will-O-Wisp, and Electric STAB complemented one another perfectly. Water STAB pressured Fire-types and Ground-immune Pokémon, making Rotom-Wash's Will-O-Wisp and Volt Switch pivoting difficult to stop. Its Ground immunity and resistances to Water, Fire, Ice, and Flying gave it plenty of opportunities to come in, making it incredibly annoying in Generations V and VI. Its Grass weakness was also very easy to cover defensively (really, teams weak to Grass were almost impossible to find). With so many important resistances and so much flexibility, Rotom-Wash became a universal utility pick. Like Scizor and Landorus-Therian, it was a plug-and-play Pokémon with an enormous presence (the three together already made a solid defensive core).
In Generation VII, Rotom-Wash dropped to UU for the first time. It had not been directly nerfed, but the burn nerf undeniably dealt it a devastating blow-burn now posed far less of a threat to Pokémon that did not rely on physical attacks (and Misty Terrain played a part, too), directly affecting Rotom-Wash's damage output. The arrival of Z-Moves also naturally posed a major threat to Rotom-Wash, whose resistances still left plenty of gaps. Once Landorus-Therian gained Rockium Z, Rotom-Wash could no longer claim