In Borderlands 1 I had a great pistol which only had a 2-shot clip but reloaded almost instantly and it also regenerated ammunition over time, fast enough that it basically had infinite ammo. I haven't found a gun in BL2 that has this ability, are there any? I'm playing as Commando and I've noticed Gunzerker class mods that seem to grant this ability, but I was hoping there are guns that do it too. The need to stop questing and go searching through containers for ammo or find an ammo vending machine is a little annoying.
There is one gun that exists that doesn't have "ammo regen", but doesn't consume bullets.
The Infinity pistol, taken from the wiki:
As an extra note, you'll need to have at least 1 bullet of pistol ammo, or the infinity will not fire.
If you decided to buy the Ultimate Vault Hunter Upgrade pack, which not only grants you a bigger level cap (Level 61), it also grants the ability to find Pearlescent weapons.
IN regards to this question, the only known Pearlescent weapon that regenerates ammo is the Avenger, a Tediore submachine gun that regenerates ammo slowly. So yes, there is at least one gun that does regenerate ammunition.
Taken from the wiki:
Near as I can tell, no there are no guns with ammo regen.
A quick Google search turns up many similar threads, obviously people are missing it from Borderlands 1. Some alternatives:
The Butcher pearlescent shotgun has an indirect type of ammo regeneration. Special weapon effects from Borderlands wiki (emphasis mine):
Items that can regenerate, add ammo or give more ammo capacity: