My favorite would have to be cats, my least favorite is mice. I don't like any of the mice and the one I have in my village right now is super annoying.
Hmm, I don't think I could pick one favorite species, but cats, rabbits, goats, koalas, squirrels and wolves are at the top of my list. As for my least favorites, I'd go with gorillas, anteaters, hippos and rhinos.