This is the full set of the Death Knight's 'armor set'. While it doesn't confer a bonus as a set, there's definitely a +Cool factor. Death Knights acquire this entire armor through questing in the Wrath Beta.
After a long chain of quests, Death Knights get to choose either of these weapons. Matthew Rossi thinks the axe looks more like a soul harvesting implement, while Elizabeth Harper and Daniel Whitcomb both feel that the sword is more Death Knight-ish.
As awesome as these cloaks look, they don't really match the armor set... except for the blue one. Yep, Death Knights get blue cloaks, too.
Death Knights not only get a full set of armor, they get a PvP trinket, too. They also get rings, a necklace, more trinkets, and a relic -- all from questing. Hate Death Knights yet?