A lot rumors and speculation as to what Batman is holding during the scene in the official Batman v Superman: Dawn of Justice teaser trailer, where he’s looking up as he stands in the middle of an abandon building.
For whatever reason since it shaped oddly and doesn’t look exactly like the rifle he’s seen holding in one of the scenes in the trailer, people have speculated all kinds of ideas as to what that oddly shaped thing in Batman’s hand is.
The easy answer and most likely– it’s a Black Rifle soft case for his rifle he’s seen holding, and we speculate he’s most likely going to use it in that scene to go where he wants to go–UP. Now the reason why we say this is only because the rifle in The Dark Knight Returns was used as a harpoon/grappling hook, which Batman used to hook himself on to a helicopter. Knowing that, most likely the rifle will end up being another form of a grappling hook for Batman in Batman v Superman: Dawn of Justice like it was in The Dark Knight Returns.
As for the case, we did a bit of looking around the interweb and found a case that looks pretty similar in shape to what Batman is seen holding in the trailer, it’s called Tactical Crusader TC48BK 48 inch Sniper Rifle Case.
Not saying it’s the same one, but it looks a lot like it when we compared it to the one seen in the trailer, in both shape and size when scaled down in photoshop:
To some fans this might sound pretty boring, that what Batman is seen holding is his rifle that we’ve already seen, simply in a case. But that’s most likely what it is, because sometimes the easy answers are the right ones.