Borderlands 2 Unkempt Herald/Fastball Farm

After completing & turning in the side mission "In Memoriam", you can farm both Boll & Savage Lee for two of the best weapons in the game.  Boll has a chance to drop the Legendary Fastball grenade mod (4 types- Corrosive, Explosive, Incendiary, Shock) & Savage Lee has a chance to drop the Unkempt Harold of which the Double Penetrating variant is the most desirable. Also, while Savage Lee always spawns in the Marrowfield, he also has a chance for a second spawn in one of two locations behind the Three Horns Divide fast travel station. If red dots/enemies appear on the mini map when spawning in at Three Horns, then it means that Savage Lee has also spawned at that location. On this run, I was lucky enough to get the double spawn of Savage Lee (though no Unkempt Harold) & I also managed to get an Incendiary Fastball.