The reward for Nightfall is the Exp / Rep buff for the rest of the week. Anything else is a gift from RNGesus. You want to run Nightfall with 2 or 3 characters every week and get a kick-ass gun or armor for each completion? In three weeks you'd be complaining that there aren't enough exotics in the game because you have them all. Play for the buff [u]and[/u] the [u]potential[/u] for a cool reward.