I'm working on a gun mod, among many others, for something approaching a Fallout setting for D&D. Magic is still there in full force, as evidenced by the thread name. I've set a rule so that any special ability that adds damage, barring standard magical enhancement (+1 to +5), cannot be added to the firearms themselves and can only be placed on ammunition. The ammunition can have these effects added cheaper than normal for the (hand waved) reason that their construction allows the easier inclusion of magical components. The special abilities Distance, Speed, and Brilliant Energy can be added normally and Ghost Touch is also possible and it adds the effect to ammo fired. Now for the ones I have so far:

Loud: Occasionally the gun going off becomes incredibly loud, dealing 1d8 Sonic damage to everyone, save the shooter, within 15 ft. Occurs during a critical hit and occurs once regardless of how many rounds are fired in the action.
Minor Evocation; CL 7th; Craft Magic Arms and Armour, Sound Burst, Price +1 Bonus

Adjusting: The gun magically adjusts the size of all necessary parts to accommodate the use of any type of ammunition used by firearms of its class(Pistols, Rifles, Shotguns, SMGs, or LMGs).
Minor Transmutation; CL 7th; Craft Magic Arms and Armour, Shrink Item, Price +2 Bonus

Scrupulous: Any round fired from the firearm may only strike a predetermined kind of enemy in the same way as the Bane ability. This ability can be toggled as a free action once per round. Firearms with this ability do not ignore armour, shields, cover, or other problems; only targets that would normally obstruct your shot.
Major Abjuration/Divination; CL 13th; Craft Magic Arms and Armour, True Seeing, Repulsion, Price +3 Bonus

So, now my request: I'm trying to come up with some new special abilities to be added to the guns themselves, as well as ideas for specific magic weapons akin to things like Flame Tongue and Frost Brand.
Also, if there is any other information you think I should have included here or that you'd like to know please let me know and I'll post what I can.