The End of Time (Professional Level 11) had a nice touch of relaxation (though the amount of pressure during some parts was insane). Architect (Professional Level 4) was fun too. More enjoyable creative challenges, and I liked the small amount of roleplay involved (basically all the Help Triggers). Ice Cavern (Advanced Level 12) was kinda poopy, but the path I found for it (giving me a time of 11.93 I think) made it fun.
I had a great time with Mountain Climber (Professional Level 3). There wasn't anything special about it, I just enjoyed it. Alpine Heights (Beginner Level 9)has great scenery, challenge, and the way the texturing was used in some parts was fabulous. Spidermon (Intermediate Level 6) is an absolute troll. :^) Vexatious also had fun and creative challenges that I enjoyed. Korzak (Professional Level 13) was a lot of fun, I enjoyed that one. Great challenges (as well as very creative). This is my #1 favorite level in the game.
Here's mine: (I like the easy ones)
1. Learning: Super Jumps (because I'm #10)
2. Wall Climber (I used to be #9 but I got knocked out)
3. Son of a Bumper (I held an accidental WR of 3.49 all because of a bug)
I'm just a 15 year old who's been playing MB for over a decade and can be annoying at times.