Tobaku Mokushiroku Kaiji

Ne'er-do-well Kaiji Itou's shiftless existence is suddenly rattled by a visit from the yakuza. Burdened by debt and resentment, Kaiji is coerced into gambling for his worthless life. As the stakes grow higher and the rules become increasingly more bizarre, Kaiji must finally take the future into his own hands!
(Source: Denpa)
Note: Won the 22nd Kodansha Manga Award for general manga in 1998.