Mew

Mew is one of the most versatile support choices in the Doubles OU metagame, thanks to its large movepool, decent bulk and relatively high Speed. Its main uses are providing Tailwind, setting up entry hazards like Stealth Rock, and helping Pokemon such as Dragon Dance Zygarde and Kyurem-B set up with moves like Fake Out and Pollen Puff. Mew is often used as a lead, to set up either speed control or hazards early on, or as a mid-game Tailwind enabler. Pokemon with strong spread moves, such as Choice Band Zygarde and Heatran, benefit from Mew's ability to reliably set Tailwind. Pokemon such as Genesect, Incineroar, and Tyranitar can threaten Mew with super effective attacks; teammates such as Heatran, Zygarde, and Urshifu-R can make use of Tailwind to put pressure on these threats. Due to an average Special Attack stat and lack of strong moves, Mew finds itself lacking in offensive pressure, which can allow opponents to reposition their Pokémon or set up.