Seismitoad. you can get this pokemon by evolving Palpitoad. This pokemon should learn bubblebeam, muddy water, bulldoze, and brick break.
Palkia. This can be obtained in Pearl. Palkia should learn Spacia Rend, Hydro Pump, Blizzard, and Thunder.
Suicune. This legendary can be obtained the same way as Entei. It should learn Hydro pump, Blizzard, Snarl, and Dig.
Milotic. This can be obtained by evolving feebas by trading while its holding the prism scale. It should learn Recover, Hydro Pump, Double Team, and Hyper Beam.
Sharpedo. Evolve Carvahna at level 30. It should learn Crunch, Ice Fang, Scald, and Bulldoze.
Gyarados. You can get him in the Lake of Rage in Heartgold/Soulsilver. It should know Thrash, Hydro Pump, Thunder, and Flamethrower.