cats, crows, ravens, and owls are common. other neat animals could include opossums, foxes, deer, rabbits, bats, and pretty much anything else. it would also depend on where the witch lives. i was thinking of a forest in america or europe, but an african witch could have a hyena familiar, or an asian one a tanuki. looking into folklore about different animals could help you too if your witch lives somewhere that you don't know a lot about.