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. 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.

The main plan with sharpshooter is to get enough damage where knockback is guaranteed. Son of a bitch might sound like a good idea, but Whizkid 1 is actually better. Power mods guarantee +1 damage just like SoB does, but whizkid 1 gives you the ability to put two extra power mods on for +4 damage, not just +1. Once your pistol has 3 power mods on it, you can either get SoB if your damage is still too low (unlikely), whizkid 2 for a couple of bulk mods, or finesse/reloader to get your knockback shots happening more often.