Bring Little Jesus Mordino's briefcase to Metzger
Go talk to Little Jesus Mordino in the Desperado casino of New Reno. He will offer your a job: deliver a briefcase to Metzger, the slaver in The Den. Note that you will have only on chance. If you lose the briefcase, the quest is lost for ever (and other Little Jesus's quests as well). Surprised that you are alone for the delivery, Metzger will give you a shotgun and few ammo to defend yourself against the wasteland. Go back to Little Jesus Mordino to complete the quest.
Prerequisite: at least 4 in charisma or intellect
Reward: a shotgun, few shells, some caps (according to your charisma) and 800 exp from Metzger. 1500xp from Little Jesus Mordino. Your reputation will increase by 150points with slavers, decrease by 200points with Regulators and people will consider you as a slaver.