I think that the sameness of the guns was a big issue with immersion -raiders in a wasteland.. and gods knows why; they're all equipped alike like some modern millitary force. There should have been dozens more of each type of gun, even if they're more of less similar.
Fallout has the Desert Eagle -and you would encounter them in bulk where you were supposed to encounter "dudes with heavy pistols". Instead, have one with a .357, one with a .44 S&W, one with a Desert Eagle, another Deagle with a long barrel (It IS a popular gun), a .44 Automag, and the leader should carey a .475 Wildey Magnum (most powerful pistol in the world). You get the picture. Also, this throws the player a curve ball; since the somewhat-alike pistols have slightly different aspects (power, magazine capacity, ability to penetrate body armor, etc.) the player no longer knows exactly what his foe is after he kills one.
Admitedly there were enough SMGs in Fallout 2 that this could happen in places (I think the Vault 15 raiders exibited some good variety amongst their arms), but everything was earily alike.