I dunno. It's just always been a wolf for me. When I see me tranformed into an animal, it's always been a wolf or a big wolf-like dog. Ever since I was a little kid. No, no... don't read into this any "lone wolf" metaphors or psychobabble. I just always liked wolves.
:)
Well, sometimes it's a black panther.
Now, if we wander into the mythological, then it's usually been a griffin or dragon... or a black unicorn.