If you want to limit this to a single transaction, the Indiana Pacers' decision to move their starting lineup anchor for a raw, unproven, skinny, 21-year-old "power" forward has to be the team's best trade. Moving Dale Davis for Jermaine O'Neal allowed the franchise to seamlessly bridge their 1990s success into the next era to the point that they won a team record (in its NBA era) 61 games in 2003-04.
But another series of transactions involving Mark Jackson may be even more impressive.
In 1994, the team acquired Jackson for the first time, sending Malik Sealy, Pooh Richardson and Eric Piatkowski to the Los Angeles Clippers. Then, two years later, the team decided that it could do without Jackson and moved him, along with Ricky Pierce and a pick, to the Denver Nuggets for Jalen Rose, Reggie Williams and a draft pick (which it used to take Erick Dampier).
Soon after, Indiana realized the error of its ways.
The team called Denver back the next year to ask for Jackson back. The Nuggets said, "Okay," and sent Mark back to Indiana, along with LaSalle Thompson, in exchange for Eddie Johnson, Vincent Askew and a second-round pick.
Meanwhile, in a separate deal, the Pacers flipped Dampier (and Duane Ferrell) to the Golden State Warriors for Chris Mullin.
So, by exiling Mark Jackson for a few years and parting ways with a series of aging vets and a few picks, the Pacers were able to put Jackson, Rose and Mullin next to Reggie Miller in their perimeter rotation as they ascended to their greatest heights in the late 1990s to early 2000s.
Pacers GM Donnie Walsh earned a reputation as one of the best executives in the league for the way he built the Pacers in the 1990s. You don't need to look much further than this series of moves to see why.
This may have been his finest work.