He can teach you archery, and this can be exploited for infinite archery. In principle it could be done with any follower who teaches something (unless Bethesda patches it).

You tell him to follow you. Then you have him teach you archery, for money. But then, since he's following you, you can take the money back from his inventory (it's not considered stealing according to the rules, because he holds your loot). Then repeat ad nauseum.