
thoynan |

Blunderbuss/Axe musket, strength power attack build. Maybe mysterious stranger and that rage power yell thing, take lots of intimidate.
Also dipping Musketeer Cavalier, trophy hunter, or spellslinger (you can burn your spells for a gun buffs for 1 min) for free gunsmithing and a free gun, well, except for the trophy hunter.

Adam McPoe |
You can easily make a thematic 'barbarian' gunslinger, but the problem comes with that barbarian is a devastating melee class who can tank a lot of damage.
On a side note a racial archetype for Ratfolk called the Gulch Gunner could be sort of the thing you are looking for. It makes a melee focused gunslinger who actively tries to provoke Attacks of Op. in order to regain his grits instead of crits. Nothing about the class screams 'only rats can do this' for example they will fire their gun at some one and then burn them with the hot muzzle. (The class for ref. can be found in the Advanced Race Guide and can be found with a quick google search of "Pathfinder+Ratfolk+Gunslinger"