Flintlocke's Blasthammer

Flintlocke's Blasthammer is a gun that is available to both factions. It is the only weapon to have the same skin as Blunderbuss of Khaz Modan, an Alliance-only weapon.

Source
This item can be found listed on the Black Market Auction House by Fargo Flintlocke for the opening bid of. It can also drop from a Unclaimed Black Market Container.