In SiT, halflings are the only ones proficient with pistols. And there’s those among them who are incredibly lethal with their gat. There’s two fighter sub-classes from Unearthed Arcana (testing material) that can make awesome pistoleros!
It is described as a sniper but in fact, its features doesn’t help at all for long-range. That looks like bad designing IMHO. But! The way it is done? It’s an excellent sub-class for fighting in a dense/urban environment.
Switch arrows for bullets and there you go… An Arcane Gunner!