Here's some ideas for a few more obscure Pokemon from Gen 3
Dewgong: Rest, Sleep Talk, Surf, Ice Beam, Hail, Rain Dance, Hidden Power Ground, Toxic
Seaking: Agility, Surf, Ice Beam, Toxic, Supersonic, Double-Edge, Horn Drill
Aerodactyl: Swords Dance, Agility, Rock Slide, Rock Tomb, Fly...