Gunslinger

Oh God yes.

Historically, gunslingers were the rough-and-tumble frontier men of the old west, where, armed with the two most famous guns ever made, the Colt revolver and the Winchester rifle, they fought the natives, the animals, and one another in the name of Humanity Fuck Yeah.

Culturally, the gunslinger was the American equivalent of the old stories of the European knight-errant, wandering from place to place righting wrongs and shooting bandits. One famous aspect of these stories is the quick-draw duel, where two men stand in the street at high noon (when everyone knows to get out of the way and the sun is be in neither of their eyes), and stare each other down, each waiting for the other to draw first so that he will have the benefit of arguing "self-defense" in court after the duel is over. In most, but not every case, the villain draws first, but the hero is faster than him and kills him.

Just like the medieval knight underwent a series of anti-heroic revisions recently, the cultural myths around the gunslingers of the old west have been reexamined in a number of "revisionist" (read: realistic) Westerns that paint them in a more morally-ambiguous light.

Pathfinder

Pathfinder actually had the balls to add gunslinger as a character class in a world of knights and swords, because fuck Medieval Stasis. They're built on the "fighter" template, so they get lots of hitpoints and lots of feats, and they enjoy a resource pool called grit that they can use for various effects. Grit is actually regenerated by doing badass deeds of derring-do more than by rest, so shooting out chandeliers, challenging villains to quick-draw duels, and leaping sideways through the air while firing are all heartily encouraged.

More than perhaps any other class, gunslingers benefit from Pathfinder's "archetype" system. One gunslinger class feature basically lets the character pick a gun off a rack to start the game with (since, otherwise, you'd have to spend more money than the entire party probably has at character creation to buy a single weapon, let alone ammunition), and sticking with one type of gun and picking an archetype to go with it is very advantageous. Musket master gunslingers get lots of free reloading powers, pistoleers get extra damage, siege gunners get to be cannon fighters, etc. Note that there isn't really a good "holding a pistol in each hand" build, so it's probably best not to try.

Your firearm is your friend and your bosom buddy. You probably won't be starting out with a multi-shot firearm for balance, and getting one later is pretty iffy, so making reloading as quick and easy as possible is absolutely paramount. Take the quick reload feat if your archetype doesn't already come with one, and take ranks and ranks of the Craft: Alchemical skill so that you can make your own alchemical ammunition. Nope, just need one rank and you can make any alchemical cartridge for half its cost and with no crafting roll, meaning you can put the rest into Acrobatics, or Stealth, or something more immediately useful, although you still want to make that alchemical ammunition, which, even when it doesn't have any special powers, further reduces the time necessary to reload a weapon. Getting it down to a free action by the time you can take multiple shots per round is important. Also, when you inevitably roll a critical fumble and your gun breaks, don't be stingy with your grit. Doing a quick clear may cost you time later, but it will save your goddamn life now.

They also manage to sidestep most MAD problems, since, although they need more WIS than the average fighter-derivative for grit points, they need less STR if they aren't lugging around an artillery piece. And even then, there's a dirt cheap magic item called Muleback Cords that can easily get around that problem.

However if you want to go the whole John Woo, Man with two Guns route, you're either gonna have a bad time, or pray that your DM/GM is lenient. See the problem is that all one-handed firearms (even the tiny ones that you stick in your pocket to hide) count as one-handed weapons (No Duh I hear you shout), and reloading requires one free hand, this means that unless either your DM/GM wants to make certain firearms Light weapons for the purposes of TWF and you have some method of getting extra arms or a tail that loads your gun for you, TWF is chock full of penalties that even attacking against Touch AC won't help you get those hits, or you take the feat which is not really worth it at early levels, and outclassed by other feats at higher levels. Probably the only real way around it is to have an extra limb, and the only way to do that without multiclassing to an alchemist or witch is to play as a Kasatha for their four arms, or Tiefling/Kobold who both have alternative racial traits that allow them to use their tails for such things.

Clear this class with your GM/DM because as with as many problems as it has, the insane cost, the difficulty of TWF, the relatively low damage that firearms do even at high levels, these weapons almost never miss due to attacking Touch AC, and most DM/GM's are not quite ready for this method of attack from anything otherthan a spellcaster, and most will balk at 'balancing' this against other easier to mitigate forms of martial prowess.

The Classes of Pathfinder 1st Edition
Core Classes:	Barbarian - Bard - Cleric - Druid - Fighter - Monk Paladin - Ranger - Rogue - Sorcerer - Wizard
Advanced Player's Guide:	Alchemist - Antipaladin - Cavalier Inquisitor - Oracle - Summoner - Witch
Advanced Class Guide:	Arcanist - Bloodrager - Brawler - Hunter - Investigator Shaman - Skald - Slayer - Swashbuckler - Warpriest
Occult Adventures:	Kineticist - Medium - Mesmerist Occultist - Psychic - Spiritualist
Ultimate X:	Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante