Great mobbing build. Focuses on splash damage, with ammo and shield endurance.
Slot1: Engulfing Kravvy Ogre Slot2: Venomous Hornet (Corrosive) Slot3: Stimulating Protuberance (Any element, but Electric and Fire work best) Slot4: Hansom Jackhammer (Fire or Electric).
For grenade mod, I like a MIRV-Tacular Hex (Electric), but use your favorite. Fire grenades are monsters with this build.
Also a good build for Heavy weapons. The blast radius for a Stuffed Quadomizer is insane, but most Heavy weapons don't dish out DPS fast enough for me.
Shield, Artifact and Class Mod
Shield: Transformer (or anything with Absorb) Class Mod: Mind Sweeper (Look for Splash Damage) Artifact: Use your favorite, but I use Commander Planetoid (Look for Magazine Size and Splash/AoE)
The main focus is splash damage, so go nuts with splash weapons, and spam grenades. If you have more than 8 nades built up, you're not throwing enough. Guns with Fire damage are greatly enhanced with this build, but if you are having trouble staying alive, you can sacrifice some damage dealing for tankiness by using more splash electric weapons to build up your Transformer shield, like the electric Hansom Jackhammer or Protuberance. When your shield drops and you need it back quick, splash damage yourself with an electric weapon and keep going. I charge head first into big enemies a lot with the electric Protuberance.
You can sub in Devistator, Devoted, Bearcat, Flakker, any Maliwan or any Torgue guns. I like grenades with Homing, and Hex or MIRV, but your splash radius will be so big, it's hard to miss. With the large amount of explosions and visuals it's hard to be accurate, so homing nades help a lot. I rarely use the Iron Bear, but having splash damage mini guns can get you out of a pickle.