I know that BL1 had ammo regen class mods and plenty of infinite ammo Orange-rarity guns, but I haven't seen even a trace of such items existing in BL2 outside of Salvador and that one unique Vladof pistol.
I got a pistol recently, orange quality, called something Infinity, don't have the game up atm. It has a 1 for the clip size and shoots without the need to reload. But when you zoom in it shoots in the infinity pattern, sideways figure eight. Pretty good gun for close engagements. I'll post stats next time i check it out.