Very often I get Strange Coins or Ascendant materials. The best week I have had for Nightfalls was the week the DLC launched. I got 2 exotics from the 3 Nightfalls I did, however they were both Exotics I already had (both Hunter helmets, and my Hunter has since been deleted in favor of another Titan anyway, but I still got exotic shards for them). I have got a total of 5 (that I remember) Exotics from Nightfalls (and I have done 2-3 a week every week, except week 1). I have got Mask of the Third Man twice, Achlyophage Symbiote twice, and Hard Light once. If it isn't materials or a repeat Exotic then I typically get a Legendary weapon that rolls with extremely bad stats. I can't remember a single Legendary weapon that I have received from a Nightfall that I went on to actually use because they roll so bad, although that falls into line with all other Legendaries I get (I really can't remember the last time I had a weapon roll with Field Scout or Persistence or Glass Half Full or Perfect Balance).