Here are my top 3 for each type (leftmost is favorite).
Normal: Togekiss, Blissey, Snorlax
Fighting: Machamp, Scrafty, Mienshao
Flying: Braviary, Swellow, Staraptor
Poison: Drapion, Muk, Tentacruel
Ground: Gliscor, Gastrodon, Donphan
Rock: Rhyperior, Golem, Rampardos
Bug: Yanmega, Scizor, Heracross
Ghost: Golurk, Gengar, Mismagius
Steel: Aggron, Skarmory, Escavalier
Fire: Infernape, Volcarona, Houndoom
Water: Kingler, Feraligatr, Milotic
Grass: Lilligant, Sceptile, Roserade
Electric: Electivire, Magnezone, Lanturn
Psychic: Gardevoir, Beheeyem, Gothitelle
Ice: Froslass, Vanilluxe, Mamoswine
Dragon: Salamence, Garchomp, Altaria
Dark: Weavile, Absol, Mandibuzz