Quickdraw (5e Subclass)
From D&D Wiki
In the early days of firearms they were a novelty, and even more of a novelty was to watch a pistol duel or a long ranged shot from a passing stranger. The man who was quickest on the draw kept his life and his reputation and the man whose aim was deadly often found himself with an abundance of high paying work. The Quickdraw exemplifies this lifestyle.
You gain proficiency with firearms and gunsmith’s tools.
Starting at 3rd level, you have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.
Starting at 9th level, you gain advantage on and may add your proficiency bonus to initiative rolls.
Damn Fine Shootin
At 13th level your reputation lends itself to your performance, allowing you to add your charisma modifier to attack and damage rolls made with a firearm. You also gain proficiency in performance if you did not already have it.
Starting at the 17th level, when you attack and hit a creature that is surprised, it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage of your attack against the creature.