A Pair of Dead Desperados, II

 is a free quest in Fallout: New Vegas.

Quick walkthrough
Talking to Sammy and Pauline Wins reveals that it was them who looted the Vikki and Vance Casino back in Primm. They will tell the Courier of their ambitious plan to rob all the casinos on the Strip, and the player can either tell them that's the worst plan they've ever heard, or pass a Speech check of 55 to tell them that the player thinks that the plan is great. Doing this will cause Sammy to give you the combination to the safe containing Vance's Gun.

Alternatively, the player can simply gun them down for some unique hats.