Years: 1976-2012
Record and Accolades: 1335-1063 (.557 winning percentage), All-Time leader in regular season wins, 3x Coach of the Year (1983, 1985, 1992)
He's the winningest coach in NBA history, and, thanks to that fact and the dearth of championship rings on his fingers, pretty clearly the greatest coach to never win a title. His teams (he coached in Milwaukee, Golden State, New York for a hot minute, Dallas, and Golden State again), almost always featured an up-tempo style, which led to a bunch of regular season Ws but also playoff disappointment. Still, the guy who introduced the league to Run-TMC and helped Steve Nash become the Hall of Famer he is today is one of the coolest coaches ever, rings or not.