This immediately brought to mind the unique pistol Ruin of House Isner from Caves of Qud:

The seven lords of House Isner feasted on boar gut and swilled wine from gilded cups in the ivy-strewn halls of their hold. They spared no concern for temperance, for the coffers of their house had swelled with gardeners’ gold amassed through the sale of water drawn from the lords’ wells. But as the gluttonous barons counted seven amongst their clan, so had become numbered their days of debauchery when the son of a beggared gardener swore a vengeful oath in the name of his father against the house of Isner.

The penniless boy beseeched a gunsmith of great repute to craft for him a pistol of the most exquisite artistry with which he could be sure to vanquish the seven lords, and in return the boy promised the smith all the spoils of the battle. The smith, who in the hazel eyes of the boy beheld the spirit of vengeance, agreed.

And so the boy, armed with the masterwork pistol, cast open the doors of the Hall of Isner with a fury that shook their iron hinges and seized upon the supping lords. Before any of them had yet set down their gilded cups, the boy unholstered the pistol and shot dead six of the sons of Isner. The last lord rejoiced at his fortune and reached for his hip from where he would sling a pistol of his own at the spent boy.

But as his crooked finger freed his holster’s strap, the boy shot the lord between the eyes, for the smith had crafted for the boy a pistol with seven chambers and seven slugs. Such it was that on this day the house of Isner fell.