Gunslinger/Fallout: New Vegas

Gunslinger is a perk in Fallout 3, Fallout: New Vegas, and Fallout 4.

Fallout 3 and Fallout: New Vegas
While using a pistol (or similar one-handed weapon), the chance to hit in V.A.T.S. is increased by 25%. As with all perks that increase the chance to hit in V.A.T.S., this bonus is multiplicative, not additive.

All of the following weapons in Fallout 3 are affected by Gunslinger. All unique variants of the following weapons are also affected by the perk:

All of the following weapons in Fallout: New Vegas are affected by Gunslinger. All unique variants of the following weapons are also affected by the perk:

Fallout 4
Each rank of Gunslinger increases damage with non-automatic pistols by 20%, meaning they do 100% more damage at rank 5. The fifth rank also increases the chance of non-automatic pistols disarming opponents.

All of the following weapons are affected by Gunslinger. The bonus is lost if they are modified for automatic fire.