So here's a look at the gunslinger. I'm not sure if Pistolero is going to be errata'd but the way it is now, the Pistol Training ability that gives dex to damage does
not overwrite the gunslinger's 5th level ability as the musket master archetype does. That's what lead me to take a closer look at this class, well that and the image of a gunslinger knocking a giant prone then headshotting him... yeah.
Pathfinder Gunslinger
Archetype: Pistolero
Race: Human
Grit: = to Wis modifier
Feats:1) Exotic Weapon Proficiency (Firearms)[Gunslinger], Point-Blank Shot, Precise Shot (human)
3) Rapid Reload (Combat)
4) Two-Weapon Fighting
5) Weapon Focus (Pistols)
7) Rapid Shot
8) Improved Critical (Pistols)
9) Double Slice (Combat)
11) Signature Deed (Up Close and Deadly)[Pistolero]
12) Signature Deed (Twin Shot Knockdown) [Gunslinger Extra Feat]
13) Improved Two-Weapon Fighting
15) Desperate Battler (Combat)
16) Deadly Aim (Combat)
17) Greater Two-Weapon Fighting
19) Improved Intiative
20) Hammer the Gap (Combat)
Deeds:1) Up Close and Deadly
3) Gunslinger Intiative
7) Deadeye
11) Twin Shot Knockdown
15) Evasive
19) Cheat Death
Breakdown:At 1st level, you can shoot into melee without fear of hitting your allies, yay!
3rd) You can reload as a free action, will always be handy
5th) you get double dex to damage (Gun Training from Gunslinger and Pistol Training from Pistolero)
9th) Amazingly, due to the way this feat is worded, you get to add your strength modifier to your second weapon. Get at least a +1!
11th) You get a good damage boost as every shot now does an additional 1d6 damage using the Up Close and Deadly deed.
12th) Every time you hit a creature twice, they are automatically knocked prone without a save!
Attack:Weapon Focus +1
Point Blank Shot +1
Desperate Battler +1
Damage:Point Blank Shot +1
Double your Dexterity Modifier +10 (aim for a +5 dex by level 5)
Strength Mod to damage +1 (at least)
Up Close and Deadly every round - +1d6, 5d6 each hit at 20
Deadly Aim - power attack for ranged, +10 max damage at 20
Desperate Battler +1
Total: 1+10+1+1d6+8+1=21+1d6
Max at 20: 1+20(from a 30 dex)+3x3(strength)+5d6x8+10x8(deadly aim)+1=351
(not counting +'s from magical firearms or multiple shots from either a revolver or a pepperbox)
# of attacks:1-4: 1 attack/round
5: 2/round with -2 to attack from Two-Weapon Fighting
6: 3/round from BAB
7: 4/round (with Rapid Shot)
11: 5/round with another BAB
13: 6/round with Improved Two-Weapon Fighting
16: 7/round with another BAB
17: 8/round with Greater Two-Weapon Fighting
Notes:There is some argument as to whether or not pistols count as light weapons. As far as it looks by RAW, they have no category classification. If you can talk to your GM and agree upon saying that they count as light weapons, then TWF is a go.
Also, here's a couple Alternate Gunslinger builds:
Alternate Gunslingers:Fighter 7/Gunslinger 13
Use the Two-Handed Fighter Archetype so you can add double your strength damage and your dex to damage to all of your two-handed gunslinger weapon attacks
Paladin 2/Gunslinger 18
Use the Holy Gun Archetype of the paladin to get a ranged smite evil
Ranger 4/Gunslinger 16
Uses the Falconer Archetype of the ranger to be able to make touch attacks at anything within 2 ranges of your weapon without using grit against your favored enemy
Feel free to post ideas!
Edit: This character has an an extra feat due to getting ewp(firearms) automatically, I wasn't counting that in. Switched feats around and added in Improved Critical (Pistols)
Edit 2: Switched Weapon Focus and Imp Critical feats around