I have a lot of favorites, but if I were to create a list of top ten, the Pokémon I would imagine to stand above all is likely going to have to be Vulpix.
It's super-adorable, and I generally find it very tough to not like it, haha. Not only that, but it also evolves into Ninetales, which is my second most favorite; Ninetales is beautiful-looking, in my opinion, and along with that, it seems to have some great battling capabilities. It has Drought ability, allowing the Pokémon to set up sun as soon as it's sent out on the field. Then, Ninetales is able to take advantage of this situation and wreak some major havoc with all its fire-type attacks.
Aside from those two, others would be Togekiss (due to similar reasons as Ninetales), Scizor, Metagross, Jirachi, Politoed, Suicune, Cresselia, and Darkrai, sorted by numerical order. Honorable mentions go to Charizard, Swampert, Blaziken, Lucario, Garchomp, Salamence, and Flygon.