Steelarrow Crossbow

Steelarrow Crossbow is an uncommon crossbow. It was tied with Ashjre'thul, Crossbow of Smiting for the slowest ranged weapon speed. Before ranged attack speeds were normalised, this was one of the most powerful weapons that a Hunter could use due to how ranged special attacks took advantage of weapon speeds.

Source
This item dropped from Dark Iron Rifleman at Dun Modr in the Wetlands.