Togekiss everyone's favorite peace loving Pokémon is back for another generation, ensuring peace by making sure the opposition does not get to attack via Flinch Hax Shenanigans. And for the most part, the generational shift has been kind to Togekiss. The Metagame has slowed down a bit, making Togekiss' speed a lot more impressive and two of the fastest threats (Hydreigon and Dragapult) do NOT want to switch into Togekiss for fear of getting wrecked by a Dazzling Gleam.
Peace and Love on the Planet Earth
Togekiss
Ability: Serene Grace
Item: Leftovers
-Air Slash
-Thunderwave
-Dazzling Gleam
-Flamethrower/Aura Sphere
Nature: Timid (+SPE, -ATK) OR Modest (+SATK, -ATK)
EVs: 4 HP/252 SATK/252 SPE
Standard Togekiss. Paraflinch between Serene Grace Air Slash and Thunderwave gives most opponents a 1 in 4 chance to attack. That coupled with Togekiss' decent base 120 SATK means that Togekiss can wear through most pokémon with ease, while providing Speed control for the rest of the team. Dazzling Gleam's merits have been epoused earlier, hitting key threats in Hydreigon and Dragapult. Last move is how you want to deal with Air Slash resists. Flamethrower is generally the preferred choice, hitting every common Air Slash resist aside from Tyranitar (and Coalossal if going down to UU) hard. Aura Sphere does hit Tyranitar a good deal harder than Dazzling Gleam, but in return you will be exposing yourself to Aegislash.
Other Options
Nasty Plot -you can forgo Speed Control in exchange for Togekiss to muscle through some bulkier opposition that may prove too resilient for normal means.
Blunder Policy -neither Air Slash or Thunder Wave have perfect accuracy and the speed boost is greatly appreciated if luck decides to go against you, but they are generally reliable enough that this is a niche pick.
Favored Partners
Dracovish - Dracovish really enjoys the speed control in Thunder Wave and anti-Dragon Presence Togekiss has. In return, Dracovish smashes through sponges, Rock types, everything. Other physical sweepers/wallbreakers complement Togekiss' special capablities.
Defog/Rapid Spin -since Stealth Rocks really chew Togekiss up, having a Defogger or Rapid Spinner is greatly appreciated. Excadrill proves to be a standout choice, as it also provides a safe pivot into Electric, Steel, Rock and Poison moves that trouble Togekiss. Togekiss in return is a Ground Immune pivot that deals with predicted Earthquakes.