The tongo wheel in Quark's Bar
Tongo cards.
Tongo is a strategic Ferengi game that is a combination of cards and roulette and is played with two to eight players. The object of the game is to win or in Ferengi terms, acquire as much wealth as possible. To participate in a Tongo game you need to have plenty of latinum. Slips or strips will suffice, but no one will stop you from betting with bars.
In general this game is only played by Ferengi, although Jadzia Dax has played on many occasions.
The four options a player has on a given turn are to 'confront', 'evade', 'acquire', or 'retreat'. Each venture has a 'risk' amount, a 'purchase' amount, and a 'sell' amount where the risk amount is equal to the sell amount minus the purchase amount.
According to Jadzia Dax, the key to tongo is "to confront when you're sure you're in a better position than the other players. And if your cards match the roll of the dice, you win." (DS9: "Meridian")
A Global Tongo Championship is held each year on Ferenginar. As of 2373 Zek had won the tournament for 17 years in a row. (DS9: "Ferengi Love Songs")
Miles O'Brien once played tongo against Ferengi privateer and a Romulan mercenary. (DS9: "Change of Heart")
Quark was on a 208 game winning streak over the period of a month during mid-2374 when he beat Jadzia for his 207th victory, causing Worf to lose a bet with O'Brien for a bottle of scotch whiskey. O'Brien enlisted Julian Bashir to help beat Quark and end his streak but Bashir failed when Quark distracted him with talk of Jadzia and Worf's recent marriage. (DS9: "Change of Heart")
During his assocation with Gaila, when he believed he might be killed, Quark made a gift of his tongo wheel to Jadzia. (DS9: "Business as Usual")