Aesthetically, my favorites are Ghost, Ice, Fairy, Fire, and Water. For competitive battling, I tend to favor Ghost, Steel, Bug, Normal, Psychic, and Ground.
Grass, Psychic, Ground, and Fire.
Ghost and Fire. My team usually ends up being mainly fire types. ==
Ghost and Dragon types are definitely at the top of the list. Mostly for aesthetics. I love the looks of those two the most. I always try to work them into my teams.
Grass and psychic. Aesthetically, I like a lot of ghost pokemon as well.

I like grass, water, electric, and fairy types.
[tot=PiplupMagby34]
i'm a water fan, but that's mainly because squirtle was my first pokemon and it was the first type i really got used to using i think.
I love fire since Charmander, burn burn burn :)
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Fairy type, of course ^_^ . I love grass and electric types too though.
I think a close second would be dragon or psychic types.
I have a preference for dark and ghost type pokemon but I definitely like psychic type pokemon (or any pokemon that can use physic type moves).
Electric, water, and dragon! I always have a combo of the 3 on my teams.
Water is always my starter, and I just love the designs of electric types. I have a shiny Ampharos on my team in X that I just adore. Also, Dragonite has been my favorite Pokémon since the beginning. c:
Probably Ghost. I use a wide variety, but I always have to have something part ghost on my team.
I always have a lot of trouble answering this question. Most of the time I'd say it was Dark, but on the odd occasion I might say Ice, or Dragon on the really rare occasion.
Probably Fire, because nearly all of my starters were Fire (I chose Oshawott as starter in the 5th gen) and Ninetales is one of my favourite pokemon. Runner-up would be Electric, with Jolteon being my all-time favourite pokemon. Other than that I have pokemon of different types in my team, because you'll never know what opponents the game will throw at you~