I would probably have to go with Wizard from Halo 1. Not really because the map was the greatest design but really because all the custom games I have played on that map. All the crazy rockets only matches, the fun shotty snipers matches and intense 1v1 CTF where just some of the times map was memorable. Honestly I have never really cared about what a map was like as long as it has good memories, was fun to play on, and was easy to maneuver.