Don't laugh, but Farm was my fav when BO2 first came out. There was just something about it that even now I cannot put my finger on, but drove me to that map day in and day out!! Visually, I think I would have to go with Nuketown. I always wondered in BO1 what Nuketown would look like zombiefied, and they didn't disappoint. As for gameplay, I would have to say Buried. I know I know, it gets boring. But you are not running miles for your next perk, the paralyzer was a great addition, also the timebomb. You can rack up the kills and hit the bomb and go back and do it all over again, maximizing your kill to down ratio