Argus' model is equipped with a large Scythe which is normally blue.
There are two color variations of the item a blue one which has a chance to drop in all difficulties and a red variety which has a chance to drop at mythic difficulty It can be randomly awarded to any class that can equip polearms, regardless of loot spec.
The Scythe of the Unmaker drops separately from Argus' other loot.
Edit: This Scythe hasn't been seen on LFR, Normal and HC (so far), so it is so it is probably Mythic-only I always enjoy it when Blizzard makes some of a boss' unique looks available to the player. This one matches the color theme of Argus the Unmaker in his Mythic-only phase.
The red version of the Scythe of the Unmaker.
Like the shoulderpads of Xavius and Garrosh Like Taeshalach from Aggramar, another weapon with a unique appearance that Blizzard is allowing us a chance to get in Legion's final tier, that drops from its raid boss wielder.
Argus the Unmaker has a chance to drop the Scythe of the Unmaker for transmogrification.
Home Argus the Unmaker Scythe Argus the Unmaker - NPC - World of Warcraf