Icebreaker from nightfall. I was so excited but thorn and thunderlord are close seconds. Only bad thing was i got it pretty close before Xur sold it so then I had to deal with all the "you're not allowed to buy things from Xur ,scrub" elitists who thought I bought it. Not that's there's anything wrong with buying weapons from Xur. However if the great gally ever decides to drop from on high that will have my best reaction