Miami Heat
The Miami Heat was good to LeBron James and LeBron James was good to the Miami Heat. Even though both parties somewhat used each other, four NBA Finals appearances and two titles are hard to top for any non-Michael Jordan run team.
If he wanted to make things right, this is one of the franchises that he still has some reconciling to do. He left the Heat in a somewhat embarrassing fashion and a reunition with the franchise would fix all the loose ends in his legacy.
Pat Riley would be able to leave on a high note, possibly delivering the Heat one more title and the fans would get some LeBron nostalgia to go with it. The Heat should absolutely be in play should LeBron want a fresh start.