They could add some cool stuff for people who have them activated. Kind of like Halo 3 with the katana.
Say you have a Warrior Class one, You get a sword strapped to your back. Or if you have the Monk one, a staff across your back. If yours is Bandit, maybe like, a mask or even a dagger on your hip.
There's endless possibilities for stuff like that if you really think about it.