Sableye

With its solid defensive typing and bulk, utility options, access to Recover, and a superb ability in Magic Bounce, Mega Sableye finds a role as a good defensive force in OU. These traits let it serve as a central pillar for stall teams and shut down virtually every Pokemon reliant on entry hazards and status to make progress except for Mega Diancie, Clefable, and Mold Breaker Excadrill. Furthermore, it is one of the few Pokemon in the tier that can reliably switch into and put a stop to Mega Medicham. With Knock Off and Will-O-Wisp, it can also aid its team in making progress against item-reliant Pokemon like Heatran and Celesteela and physical threats like Landorus-T and Mega Swampert. Additionally, it can hold off on Mega Evolving to make use of Prankster and burn Mega Mawile and Kyurem-B, two major threats to stall archetypes, in a pinch. However, there is very little that Mega Sableye can do with its low Speed, and its lackluster offensive stats leave it heavily prone to passivity, making it easy setup bait for sweepers like Mega Charizard X, Volcarona, and Substitute variants of Dragonite and Gyarados. Additionally, its typing leaves it chased out by a plethora of Fairy-types like Mega Diancie, Clefable, Magearna, Tapu Lele, and Mega Mawile, and the former three of which are not bothered much by Knock Off and Will-O-Wisp. Tapu Fini's Misty Terrain doesn't help matters much either despite not enjoying switching into Knock Off, since it cancels out Will-O-Wisp much to the appreciation of wallbreakers like Mega Mawile and Garchomp. Mega Sableye is also a sitting duck against Fire-types like the Mega Charizard formes, Volcarona, and Victini due to their immunity to Will-O-Wisp. These drawbacks limit its usage to only on stall archetypes, where they can afford the lack of momentum.