Specs Rotom-W
aka clout goggles rotom
Rotom-Wash @ Choice Specs
Ability: Levitate
EVs: 248 HP / 8 Def / 252 SpA
Modest Nature
-Hydro Pump
-Volt Switch
-Hidden Power Fire / Hidden Power Ice
-Trick
This is used as a strong pivot that can spam volt switch. It's kind of like Tapu Koko in that sense, but with much more bulk and more capability to check ground types. Rotom-W still checks a lot of the mons it normally would but gets worn down more easily, so it should primarily serve as a pivot with the occasional task of checking Lando, Hawlucha, Fini, etc. It's much less likely to have its Volt Switches blocked than those of Tapu Koko since fat grounds will always be careful to avoid Rotom-W's Hydro Pumps or expected Will-o-wisps. And of course, the surprise factor is always relevant.
Specs Hydro Pump and Volt Switch hit most of the meta for big damage, including guaranteed 2HKOs on spedef Mega Sab (up to 41% with Volt), standard defensive Rotom-W, and even Mega Latios after rocks. Hidden Power Fire is the best option for the third slot since it targets all of OU's fat grass types and is the strongest option against Ferrothorn, Mega Scizor, and Kartana. However, Hidden Power Ice hits most grasses and deals heavy damage to the Mega Lati twins and other dragons. It also destroys Gliscor, Garchomp, and Landorus-Therian without risking Hydro Pump missing. Keep in mind that HP Ice still cannot 2HKO Mega Latias after rocks and that Specs Hydro Pump still has a chance to OHKO Rockium Garchomp after rocks. Trick cripples basically every switch-in so potential checks to its teammates are effectively useless.