Falcon Heavy
Falcon Heavy test flight had no contracted customer, and in order to limit the cost on such a test flight, SpaceX targeted to have reused side-boosters. Boosters B1023 and B1025 that had been flown as Falcon 9 configuration, were reconfigured and used as side boosters on the first flight of Falcon Heavy in February 2018, and then both landed side-by-side at almost the same time on the ground pads. Later Falcon Heavy flights used either new boosters, or side-boosters previously flown on a Falcon Heavy. SpaceX has been unable to recover the central core in any of the three Falcon Heavy, but managed to recover all the six-side boosters.