Palmer at the Battle Tower
1st time:Dragonite, Milotic, Rhyperior
2nd time:Heatran, Regigigas, Cresselia
Thorton at the Battle Factory
He uses rental pokemon, so what pokemon he uses is completely random.
Dahlia at the Battle Arcade
1st time:Dusknoir, Medicham, Ludicolo
2nd time:Zapdos, Blaziken, Togekiss
Darach at the Battle Castle
1st time:Staraptor, Empoleon, Houndoom
2nd time:Entei, Gallade, Empoleon
Argenta at the Battle Hall
She uses pokemon depending on the time you choose. You have to beat Rank 10 on every other type for you to appear.
Hope I helped:)