Dark and Rock

Dark: Houndoom, Shiftry, Sableye
Rock: Aerodactyl, Cradily, Aggron

Only one type, and only three Pokemon from that type? That's too hard for me.

Stan for the best type

Cloyster is the only one of those I don't really like. Starmie, Vaporeon and Lapras are my top 3. To fill out the Top 6 I'd probably go for Gyarados, Kyogre and Milotic (Staryu if NFE)

Electric & Psychic...

Electric:
- Ampharos
- Luxray; even though its moveset is
- Jolteon

Psychic:
- Alakazam
- Gallade
- Mega Metagross

WATER

Ghost and Psychic and my favorite Pokémon would be the Porygon line using conversion for those types.

If that isn't possible then I go with Gengar, Mewtwo and Giratina.

Psychic

I think either Normal or Fairy. I really like Bug too though.

I don't have a favorite type

But my favorite Pokemon are all the Legendaries and Unique Pokemon and all the shiny versions of all the Pokemon