For me personally I would like there to be the ability to shape shift to different animals, such as a wolves. Not only would this be cool but it could have other advantages and disadvantages for example as a wolf you could run faster, gain the ability to follow a scent (for example if someone has disappeared you could find them easier obviously however there would need to be a way to follow clues as well so that players without the ablity to shapeshift could also complete the quest, you could gain special attacks because obviously you can't use your sword. On the other hand you would lose ability to cast other magic spells whilst in this form, your health would drop to say 30% of your overall health, afterall you wouldn't have any armour and finally farmers may instantly attack you. Also how cool would it be to be able to transform into a eagle and fly across the map.
Now I am not saying these should be low level skills a player should have to work towards it and would need to be pretty good at magic, maybe say 75 skill points in whatever magic school it was included.
I would personally keep it only to animal forms and not shapshifting into zombies or skeletons or goblins, but your comments are welcome