It's hard to pick a specific team because I have many, literally hundreds of teams. Even when I begin my playthroughs, I always start with at least two teams. Is it alright if I list more than one? If so, I would choose:
(All-time) Favorites: Starmie, Blaziken, Serperior, Electivire, Haxorus, Gardevoir (and Lucario)
Secondary (All-Time) Favorites: Feraligatr, Machamp, Magnezone, Garchomp, Weavile, Gengar (and Alazakam)
Gen 8 Baton Pass Sweepers: Butterfree, Blaziken, Klefki, Starmie, Garchomp, Ditto (or any special and physical sweeper in my favorites list)
National Dex Baton Pass Sweepers: Smeargle, Blaziken, Feraligatr, Gardevoir, Breloom, Ditto (or any special and physical sweeper in my favorites list)
OU Balance: Landorus-T, Dragapult, Kartana, Blissey, Urshifu-Rapid-Strike, Heatran
Gen 8 Mostly Legendaries: Landorus-T, Kartana, Palkia, Heatran, Cresselia, Umbreon
Nintendo Switch Battle Stadium Ranked Battles: Landorus-T, Zacian, Ditto, Seismitoad, Zapdos, Reshiram