Gastrodon

Gastrodon has a useful niche as a defensive Pokemon in the OU metagame, boasting an excellent defensive typing, decent bulk, a Water immunity due to Storm Drain, and reliable recovery. Due to these traits, it can handle a multitude of common OU threats, including Keldeo, Thundurus, non-Grass Knot Mega Metagross, Mega Manectric, and Rotom-W, and is quite possibly the best answer in existence to powerful Swift Swim users in the rain. Unfortunately, Gastrodon's raw bulk is not exactly outstanding, leaving it unable to tank hits from Pokemon such as Mega Lopunny with even full defensive investment. It also faces some competition with other bulky Ground- and Water-types for a teamslot; though Gastrodon has a unique niche, it can be difficult to justify using it in lieu of other options at times.