Smooth-Talking Criminal

Smooth-Talking Criminal is an unmarked quest in Fallout: New Vegas.

Detailed walkthrough
Talk to Francine Garret of the Atomic Wrangler casino and ask her if there's some work to be done. This starts the larger quest Debt Collector.

One of the characters who has to pay up is Santiago, a smooth talker residing in a Squatters camp near Freeside's east gate. He is trying to talk his way out it by telling he's a VIP at the Casino and offering you a password to get a discount at Mick & Ralph's. This is just a con however, as attempting to acquire said discount will result in Mick or Ralph telling you they don't do discounts.

Believe and subsequently pay him (with Barter skill less) or use force to get the money that way.

Behind the scenes
The name of the quest references Michael Jackson's single, Smooth Criminal.