This is a replica of Batman’s Grapnel Gun from Christopher Nolan’s Batman Begins.
Batman’s Grapnel Gun was used by the Dark Knight to move from the ground to the rooftops of Gotham City.
This replica comes from the Noble Collection who have produced a number of props from the Nolan’s The Dark Knight Trilogy.
This is a full scale gun replica that measures 16″ in length (including a display) and weighs 8.2 pounds.
There’s a couple of these floating around, usually going for somewhere between $190 and $290 (yes, that much of a difference). The best price going at the moment is via Amazon: