Gastrodon

Gastrodon's good typing and bulk, combined with its decent movepool, allow it to be a niche check to some extremely common Pokemon in the Doubles OU metagame, including Landorus-T, Heatran, and Thundurus. Its ability Storm Drain allows Gastrodon to check rain teams and help teammates that are weak to Water-type moves avoid damage. Gastrodon's access to recovery plus its coverage movepool allow it to stay on the field many turns and deal damage to a wide variety of common threats. However, Gastrodon's very low Speed stat means it will always be moving last, and with its poor Special Attack stat, it doesn't really thrive in Trick Room; additionally, Gastrodon often relies on boosts from Storm Drain to be a real offensive threat. This lack of speed and power means that Gastrodon is threatened by strong physical attackers, such as Mega Kangaskhan, when it cannot burn them with Scald. Gastrodon also faces competition from many other Water-types, such as Swampert, which has similar typing, movepool and access to Wide Guard, and Suicune, which is bulkier and can provide speed control. Similarly, Gastrodon has to compete with other common checks to rain teams, such as Kyurem-B and Ferrothorn, which are better Pokemon overall and notably not weak to Grass-type moves from Ludicolo.