Just became champion in Ultra Sun with:
Alolan Marowak lvl 69 (relaxed)
Lightning Rod @Muscle Band (@Zoom Lens for most of the game)
Fire Punch, Stomping Tantrum, Smack Down, Bonemerang
Ribombee lvl 69 (hasty)
Shield Dust @Shell Bell
Dazzling Gleam, Draining Kiss, Pollen Puff, Energy Ball
Decidueye lvl 69 (jolly)
Overgrow @Scope Lens
Shadow Claw, Leaf Blade, Spirit Shackle, Pluck
Pangoro lvl 70 (relaxed)
Iron Fist @Safety Goggles
Low Sweep, Brick Break, Bullet Punch, Crunch
Starmie lvl 67 (naive)
Illuminate @Wise Glasses
Bubble Beam, Power Gem, Psychic, Scald
Magneton lvl 69 (jolly)
Magnet Pull @Eviolite
Flash Cannon, Tri Attack, Discharge, Thunderbolt
Decidueye, Ribombee, and Magneton were returning favorites from previous visits to Alola. Starmie is an old favorite but this is the first time I've used it outside of Kanto. Alolan Marowak and Pangoro were entirely new to me. I loved all of them; Marowak was probably the weakest team member, but she wasn't lagging behind to any significant extent, and I can't pick out any single MVP of the run.
I had horrible RNG for abilities this game; it took me like seven attempts to catch a Pickup Meowth at the beginning of the game, and at least three to find a Lightning Rod Cubone. So while I would have preferred Sturdy on Magneton and Natural Cure on Starmie, I decided it didn't matter to me enough to spend my time continuing to search.