The gun is wielded by Greg Nightmare during the first half of the final battle at the end of Smile, although here it does minimal damage to the player. When Nightmare's torso is blown apart, the gun drops from his hand onto the floor but cannot be picked up by any of the Smiths except Garcian, who then uses it to destroy the final Black Smile and finish off Nightmare for good.
It is revealed soon after that the Golden Gun was the weapon used by Emir Parkreiner during his massacre of the Smiths at the Union Hotel. On the roof of the hotel Garcian witnesses a flashback of his previous self committing suicide with the gun.
The revived Emir uses the weapon when he travels to Battleship Island three years later to eradicate the remaining Heaven Smiles, which are instantly vapourised by a single shot from the gun. Depending on the choices the player makes, he also uses it to execute Kenjiro Matsuoka. The Golden Gun is finally used in the encounter with the Last Smile, which, uniquely, requires several bullets to kill it instead of just one.
The Golden Gun resembles a long-barrelled, gold-plated revolver with a 6-bullet capacity. The reloading animation is identical to Garcian's default Walther PPK, despite the Walther being a semi-automatic pistol. Like the Walther, the Golden Gun cannot be upgraded.
- The weapon, and its ability to kill almost anything in one shot, is almost certainly a reference to the eponymous handgun featured in the James Bond film The Man With The Golden Gun.