Big Winner, Atomic Wrangler

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough
Play Blackjack, Slots or Roulette table at the Atomic Wrangler Casino, and win 1,250 to 5,000 chips in 3 stages. After hitting the 5,000 mark, the Garrets tell the player they have had enough and ask him to leave.