Minotaur Torch Hammer, Scorn lava launcher, Wretch naginata (the huge polearm they use), and HIVE BOOMER are just a handful of the weapons i would love to see brought up as either exotics or unique legendaries.
I also would like the scorn sniper rifle and sawblade launcher, and a Taken Phalanx shield (probably as a heavy "shotgun" that launches things similar to tractor cannon.
I've always wanted a special ammo rocket launcher based on the cabal. Or a special ammo sword pike the fallen use, it could have extended range but a slow swing speed. A legendary vex linear fusion would be cool to