Still waiting to use them
I think I'm gonna start a new Mordecai and exclusively use Sniper Rifles and Shotguns. Here are my thoughts on pistols:
Repeaters are only useful if they have a high rate of fire, and can be nicely effective against multiple lower-powered enemies at medium to close range.
Revolvers are hard to use, have a low fire rate, high damage, but not worth using over Repeaters unless you're a crack shot at the head from a medium distance.
As a Mordecai using a Sniper Rifle and Revolver, I found myself needing a lot of help with multiple enemies or fast enemies. It's hard when you pick off 1 or 2 enemies from long distance and get rushed by 3 or 4 more and all you have to defend yourself are your Bloodwing, Revolver, and Grenades, not to mention the point-blank no-scope sniper shots.
This way, I can have my Sniper Rifle, a nice Shotgun, a Launcher, and one other weapon. Maybe a Rifle or SMG.