Seeing your shoulders and feet if you move around.
In 1st Person, (this is probably the least likely to get picked) seeing your hair move around, yes, it's a tiny update, but could be fun, and if you're looking out of a helm, you can see the parts covering your face, example: Glass armors helmet has something to cover your eyes, if your in 1st person do you want to see that little small thing? Sure, tiny little things to do, but could add to the realism.
Post your wishes for 1st Person experience here!