If you play Destiny, how excited are you! The return of the Gjallarhorn! If you pre-order Rise of Iron you get the special edition Iron Gjallarhorn which is Black and Silver!
You don't have to pre-order Rise of Iron to get the Gjallarhorn, just the special edition!
FYI // You have to complete the special quest and make your Gjallarhorn. It doesn't drop as a reward or just handed to you.