Whimsicott is now able to use one of its arguable most important moves (Encore) with Switcheroo, as well as Memento + Switcheroo, so a set like this seems great for offensive teams:
Whismicott @ Lagging Tail
Ability: Prankster
EVs: Whatever suits your team
Nature: ^
- Switcheroo
- U-turn
- Encore
- Memento
This set plays as a check to set up sweepers and a pivot / supporter to help your own set up sweepers find the free turn they need. With Lagging Tail + U-turn you make sure that your offensive Pokemon will come in unscathed, even if the opponent is slower and decides to stay in, while you also get to pseudo-paralyze any Pokemon you want with Trick (except from MEvos, in which case you just U-turn the fuck out), and the best thing is that the opponent can't get rid of the pseudo-paralyze effect with clerics, RestTalkers, or Natural Cure Pokemon. Encore is your usual weapon against set up sweepers and Pokemon that used a harmless move, while Memento is amazing for giving your frail sweepers that one set up turns they need. The great thing about this set is that it has a lot of utility throughout the whole game, as Whimsicott now checks a lot of Pokemon with its great typing (Dragonite, Garchomp, Zygarde, Landorus-T, Terrakion, Keldeo, Rotom-W, Gliscor, Breloom, Gyarados, Klefki, Latios, Latias, etc) and is thus able to force a lot of switches and get a lot of momentum for its team with U-turn, cripple one Pokemon in each game almost guaranteed (Trick), stop set up sweepers, and give one guaranteed set up chance for your own set up sweepers. This thing is like a box of candies for offensive teams.