Of the levels types, it'd be interesting to know what people prefer to play.
The major groups include Environmental, Challenge, and Misc, but let's not forget Puzzle, Maze, Trick Jump (not an official category), and Playground, too.
Please mention your favorites, and if possible, why you like them, or why they appeal to you.
This is more of a general opinion gathering, so you don't need to base it on anyone's specific levels. Imagine that you've played a perfect level of each type you wish to discuss; which would you prefer?
I'll start:
I seem to prefer challenges (short of lunatic). They cover a wide variety of genres and often have exciting and interesting play mechanics. Unlike a few other level types, challenges can be made from any environment and can be very realistic, bland, pretty, boring, etc. depending on the wish of the level maker. I especially like challenges that are not just jumping and avoiding things. Challenges seem the most interesting to me when they have a lot of elements from the other styles too.