"Not Full Of Monkeys" is a challenge that invloves killing enemies with stationary barrels of any type. With Gaige the Mechromancer DLC, you don't need the barrel! Anger a swarm of Rakks and summon the Deathtrap. When they rush you, the Deathtrap will use its laser to kill them. It counts as a stationary barrel this way. Try this on flying enemies for some quick Badass rank.