Strategy:Pistol Types

General

Pistols aren't very useful in general games because of their reliance on pistol-specific traits - son of a gun and dualgunner. If you aren't getting these traits, the pistol will see little use beyond level 1 - the shotgun reloads quickly enough to not need a backup weapon and the pistol is no better at very long range than the shotgun is.

However, if you get these traits and use pistols as your primary weapon outside of an Angel of Marskmanship game then they'll be rather efficient and powerful for general fighting, and you can keep a larger weapon (such as a missile launcher, powerful shotgun or BFG) for larger groups of enemies.

Angel of Marksmanship/Pistol-based characters

Pistols are extremely ammo-efficient and fast once you have a few levels of Son of a Gun. Their weaknesses are frequent reloading and poor accuracy at long range. These problems can be dealt with by getting traits, but generally modding your pistol(s) will be enough.

Fighting things one on one is more important with pistols than any other weapon - you don't have any AoE unless you get a unique pistol or something, and also reloading two pistols in the middle of a fight is a bad idea and it's something you'll have to do if too many enemies chase you down.

The most important mods for pistols depend on your master trait - but agility and bulk are good in general if you're not going for a master trait for some reason.

Pistol Marine - Bullet Dance

Bullet Dance gets your shots out faster, so you spend less time per enemy. Unlike other pistol master traits, it also allows you to take advantage of the damage boost for both Son of a Gun and Son of a Bitch. Reloading after each enemy is still an unfortunate problem, so your pistols should probably be bulk modded to cut down on that.

Bullet Dance is generally considered to be the worst pistol master trait, so it should be avoided unless you want to be a marine for other reasons.

Pistol Scout - Gun Kata

Gun Kata makes your next shot instantaneous when you dodge an attack (See Dodging), and automatically reloads your pistols whenever you kill something.

Gun Kata is probably the stronger choice of the two dual-pistol master traits. With hellrunner 2 and dodgemaster, your dodges are extremely likely to work so as long as there are no always-hit enemies hanging around you can constantly dodge and only stand still when taking free shots.

However, some attacks deal damage even when you dodge them (Arch-Vile and Revenant attacks, for instance) so you'll need HP for them, and some attacks cannot be dodged (only shotgun-based attacks).

With Gun Kata, your reloading is no longer an issue (perhaps the best part of the trait) so agility mods may serve you better than bulk mods. 12 shots is generally enough to kill anything that moves already, just make sure they all reach their target.

Pistol Technician - Sharpshooter

Sharpshooter is a single-pistol master trait. It guarantees maximum damage on all pistol shots and, because of Eagle Eye 3, might as well guarantee hits too.

Sharpshooter is the most effective Pistol master trait once it gets going. The guaranteed maximum damage will not only keep your DPS on par with Dualgunners when accounting for their varying damage and misses, but it will make your Pistols very ammo efficient, and more importantly, very reliable at being able to knockback enemies; just a single Power mod to a standard Pistol and it will be able to knockback enemies with a 2 armor value. This guaranteed damage will allow Sharpshooters to reliably kill the elite enemies in a single clip, when other Pistol builds can really struggle to do that without Exotic and Unique Pistols, and the guaranteed knockback makes Sharpshooters just as effective at Corner Shooting as Shotgun builds, while being able to be very effective at fighting enemies in the open when the knockback will push them out of vision and give you time to safely reposition and/or reload. This guaranteed damage will also allow Sharpshooters to flinch the Spider Mastermind easily and reliably, giving them a free victory against her if they get a strong enough Pistol, while other Pistol builds will struggle against her.

Another major part of Sharpshooter's strength is since you're a Technician, you can invest in Whizkid without needing 2 levels of Finesse first, not only making getting Whizkid faster but also allowing you to not need to invest in a mostly superfluous trait for Pistol builds. Since the only standard Pistol is so weak and none of the Exotic/Unique Pistols are ever remotely guaranteed to be found, modding is extremely important for Pistol builds to get stronger weaponry, so being able to get Whizkid 2 levels sooner gives Sharpshooters a serious legup over other Pistol builds. One more perk of Sharpshooters is since you're not dualgunning, you can use your prepared slot on an ammo box, and thus make reloading an almost nonissue, without needing to rely on killing something like Gun Kata does nor wasting any levels on Reloader.

The big weakness with Sharpshooter is that it's really really hard to get it off the ground. Pistol builds already have it rough in the early game, but Sharpshooters have it so brutal that they may have the hardest early game of any build, even harder than melee builds have it; on harder difficulties, you're going to have many Sharpshooters die before you ever get the trait. The first big problem is that since you can't get Dualgunner, you lose the big halfway powerup other Pistol builds get, and SoG3 alone is still pretty damn lacking; you're going to have a really hard time killing anything bigger than a Demon before it gets to you, and you are not killing bigger enemies in a single clip. The second big problem is the requisite three levels of Eagle Eye. One level in it is really helpful when it'll shore up most of the annoying yet crucial misses Pistols will frequently have, but the second level has seriously diminished returns that won't help you much when you're already hitting over 90% of your shots after the first level, and the third is flatout superfluous, while the trait is useless with Shotguns, your main supplemental weapon you'll be relying a lot on as you build your Pistols up. So in getting Sharpshooter as soon as possible, you'll be wasting about two levels that could have went to getting Whizkid to make your Pistols and other equipment stronger or to getting something like Hellrunner to help keep you alive until you get Sharpshooter. Once you get Sharpshooter it will get a lot easier and thus getting it as soon as you can is an upmost priority, but until you get it, those issues combined with the general weakness of Pistols and the inherent weakness of the Technician, will leave you with a pathetically weak character that will die ridiculously often.