Wolf and lion forms are buffs which include looking like an animal. There are also some fluff spells which allow you to look like different animals just for fun. Wardens can be bees at 30 and owlbears at 40. Furies can be badgers at 30, but I can't find what they change into at 40. (The spell is Curse of the Unnatural.)
But the ones that really matter are the wolf and lion; they also get upgraded so you're not always using your level 20 spell.