The easiest answer to this would obviously be the Gretzky trade tree, which lasted over several decades. One that hits home for me (for all the wrong reasons) would actually be the Eric Lindros trade tree. Philly would send a king's ransom to Quebec to get the rights to Lindros, including sending future Hall of Famers Peter Forsberg and Ron Hextall the other way. Also included in the trade was the 1993 1st round pick used to select longtime NHL goaltender Jocelyn Thibault, another 1st round pick, and several NHL players, AND $10 million in cash.. something not allowed by today's rules. The trade tree actually lives on today as we speak, as Arizona's Brandon Gormley is the only one keeping it alive. The tree had actually almost died back in 2009 but Calgary's Stefan Elliott was traded to acquire Gormley, keeping the tree alive by a single branch. We'll see how much longer it can live into the future.