Well, definitely Espeon, then probably Glaceon, then I'm not sure if it would be Umbreon or Vaporeon. But if there was a dragon Eevee (and it was actually done well - not like Leafeon, who should have flowers) then it would be one of my favorites. See, my favorite types are Dragon, and then Psychic. ^-^ And after that, I pretty much like anything I think looks nice... ^^" But if there was a Light type (like, the opposite of the dark type; people keep going "fire and electric" at me, but they're different - so different...) then I would also have a preference for the Light type.
Needless to say I'd like to get the light type working in my game. :D