This one seems an odd choice to put in a list of questions about a hobby normally steeped in fantasy or science fiction. I do understand that interesting fauna can be found in the various milieu presented by the world-builders of our hobby, even Khardtha has some, but today's topic kinda has me on the back foot.
I suppose my answer would be the badger. My friend Eric's wizard, Hazeem, was reincarnated as a badger once, and a few of the druids and rangers I recall over the years have had badger animal companions.
Past that, I really have no other reason for choosing the animal.
Oh, unless these are good reasons....