Pignite and Leavanny can use Tackle now, and Leavanny never used that move on-screen ever since he had evolved from Swadloon. Oshawott previously knew Tackle, although it appears that the move had been replaced with Hydro Pump in BW087. In both Pignite and Leavanny's cases, both pokemon have access to powerful moves (Flamethrower, Energy Ball) and somewhat strong moves like Razor Leaf and Flame Charge in addition to Tackle. Ironically, Pignite and Oshawott had the most development and focus out of the pokemon on his Unova team.
Snivy and Palpitoad (Ash caught him in his evolved form); they have not learned any new moves since they were caught. Snivy can still use Leaf Storm and Leaf Blade, and Palpitoad can use Supersonic and Hydro Pump.
Pikachu, Scraggy, and Oshawott-- all of whom have "character"-- have all learned new and powerful attacks ever since the start of Best Wishes!. Scraggy can now use Hi Jump Kick and Focus Blast. Oshawott can now use Aqua Jet and Hydro Pump. Pikachu can now use Electro Ball in addition to its already powerful Iron Tail and Thunderbolt moves.