LOOK at the Second Slide show! THE -blam!- IS DAT ON THE THIRD SLIDE?
He's toting a Rocket on 'is back so it's no' a Heavy.
New Relic-type object?
EDIT: Added the Photo proper.
EDIT2: Alright, very common consensus agrees. It's more than likely a Relic type item (a very fresh spin on it I might add). Can't wait to see how it works. That things' got some Dakka written on it, can't wait to see what the Super can do. Also added some profanity-safe bits.
EDIT3: New theory saying Exotic Heavy Special/Primary... Not too sure I'm inclined to believe this one. That said back to the theory of 2TIDE many are noticing it may be a portion of the Walker's main cannon.
EDIT4: Not a Titan Super sadly, the Hunter behind him's toting one too. I suspect third Subclasses sometime around Comet/following expansions.
EDIT5: I've seen multiple lads/ladies mention when Deej stopped shy of the last weapon on the Monarchy's screen: http://i.imgur.com/MGx9P6B.jpg, not to pop the balloons that's just the updated Admonisher icon. Datto can't get it right everytime. Also, in regards to the location being Winter's Lair I'd say the Sword of Crota mission comes to mind in regards to testing and playing with Relics before they're gamechangers.
TLW: Confirmation as part of the new Strike http://imgur.com/7rDNLCq Credit to Sparknish. May still be a Relic-like in PoE but who knows.
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Its gotta be crucible, to the left you see a guardian trying to shoot the titan.