I love Nebula when I'm playing spy because the launch pad can get you some nice backstabs on hale plus the big HP that's in the middle of the jump so it's hard for hale to kill you as spy and if you're a trolldier it comes in handy, so I'll say that's probably my favorite. Sky high resort is a classic and I like it, especially as the easter bunny demo in the pool whilst raging, best part of the map though is the Will5023 Smells sign.
( ͡° ͜ʖ ͡°).