Big Winner, Atomic Wrangler

Big Winner, Atomic Wrangler is an unmarked quest in Fallout: New Vegas.

Quick walkthrough
To complete this quest, the Courier needs to play the games that the casino has to offer (Blackjack, Slots and Roulette) until they are banned from gambling in the casino. They can be banned by winning too many games and getting too much money from the casino. During this process, three different prizes will be received from the casino, after the Courier wins 1250, 2500 and 3750 caps. The prizes are received automatically after reaching the chip milestones.

Detailed walkthrough
As the Courier wins the games that the casino has to offer, they will receive the below rewards after reaching the chip amount:
 * 1,250+ chips: beer
 * 2,500+ chips: whiskey and dapper gambler hat
 * 3,750+ chips: absinthe, Rum & Nuka and dapper gambler suit

After earning 5,000+ chips, the Courier will be banned from playing games in the Atomic Wrangler Casino. They can still use its other functions like the bar and the services of the prostitutes (if the Wang Dang Atomic Tango quest has been completed), but cannot gamble on its tables anymore. This ban is permanent.