Monkey Shoulder Scotch, Campari, and Peychaud's—a smoky, herbal riff on your Black Manhattan.
The Smoking Gun replaces rye with blended Scotch in a Black Manhattan framework, and the substitution is the whole point. Scotch whisky's smoke and malt sit differently against amaro than rye's spice does. Monkey Shoulder is blended from three Speyside malts: enough smoke to register, not enough to overwhelm. It is a deliberate choice. A heavily peated Islay malt would fight everything in the glass.
Campari replaces Averna as the bitter component, which pulls the drink considerably drier. The Black Manhattan with Averna is rich and dark; this version is sharper and more angular. Peychaud's bitters, originally from New Orleans, carry a herbal anise note that connects the Scotch's peat to the Campari's cherry. It is the piece that makes the drink cohere rather than just accumulate.
The result reads like a Black Manhattan's more exotic cousin: recognizable in structure, strange in character. Everything familiar has been replaced by something almost-familiar.

Pre-batch all spirits together. Peychaud's adds herbal anise.
Peychaud's adds herbal anise instead of cherry. Smoky Scotch + herbal bitters = post-dinner lean. Drier than your Black Manhattan.
Build and stir. A creative riff on your Black Manhattan.
Peychaud's replaces Angostura, adding herbal anise. This is drier and more herbal than a standard Black Manhattan.