So, after some intense debate and some "you're all idiots" discussions, we have finally come up with a list. This is completely and totally final and no amount of complaining will change it.

Bug:
Drapion, Flygon, Gliscor

Dark:
Crobat, Noivern, Gyarados, Huntail

Dragon:
Charizard, Aerodactyl, Gyarados, Ampharos, Sceptile

Electric:
Porygon2, Porygon-Z, Illumise

Fairy:
Altaria, Audino, Delcatty, Dunsparce

Fighting:
Lopunny, Pinsir

Fire:
Solrock, Groudon

Flying:
Volcarona, Scizor, Venomoth, Dustox, Mew, Beedrill, Hydreigon, Flygon, Pinsir

Ghost:
Ninetales, Absol, Houndoom

Grass:
Sudowoodo, Florges, Maractus

Ground:
Tyranitar, Shedinja, Ninjask, Cradily

Ice:
Slowking

Normal:
Clefable, Granbull, Togekiss, Azumarill, Talonflame, Jolteon, Flareon, Vaporeon, Espeon, Umbreon, Leafeon, Glaceon, Sylveon

Actual Announcement:
This is not even remotely accurate. You may now roll Underground once per forum each month.

Poison:
Gliscor, Breloom, Zangoose

Psychic:
Darmanitan, Ninetales, Golduck, Sableye

Rock:
Sableye, Starmie, Espeon

Steel:
Rhyperior, Electrode

Water:
Dragalge, Eelektross, Dragonite, Malamar, Stunfisk, Masquerain

Enjoy!