2) Gilbert Arenas
Gilbert Arenas started his career in Golden State, where, despite being a second-round pick, he quickly proved himself. However, due to cap constraints, when it came time to re-sign him, they were outbid by the Washington Wizards.
As a member of the Wizards, Arenas' career really took off. For four impressive seasons, Arenas was one of the best scorers in the NBA, averaging 27.7 points while bombing away from three at an above-average percentage in addition to 5.7 assists and 1.9 steals. He made three straight all-star teams from age 23 to 25 and looked like he was on his way to being a future Hall of Famer.
Of course that didn't happen, and he played just 47 games between 2007-08 and 2010-11 due to an ACL tear and the infamous gun incident that resulted in a big suspension.
When he did finally play again, he was a shell of his former self and was shipped out to Orlando, where he lasted half a season before finding his way out of the league by the age of 30. Few players can say they were as explosive of a scorer as Arenas was at his peak but few flamed out as spectacularly as he did.