The riddle Probably the most genius riddle ever, this riddle makes you want to slit your wrists more than a WooHooII level but makes enough sense to be able to solve it. (no offense WooHooII!)
Euphoria Do I need to say anything about this level that has already been said? this level is all in all a master piece for the shrooms effect alone!
8 Simple deaths DemonicYoshi + simple concept = genius level Way to take a rather simple concept and turn it into a masterpiece!
A vertical world The concept may not be fresh, but the world looks epic, and it's obvious that ferrari put a lot of time in that level!
The paranoia series By many to be their favourite trilogy, the paranoia series is a sinister story about someone that needs your help getting back to where he was...
The BL bomber series DemonicYoshi isn't the only one to turn a simple concept into an epic series of levels, every level adds somethings new so you never feel like it's the same thing over and over.
Waterworks This proves that allyally, Elizea and lololol collaboration turns out well! Every part of the level feels great, the whole levels is so detailed into the physics and the gameplay is exquisite as well.
Honorable mentions: Arbitrary Arena - Classic WooHooII level Falling Up - One of the coolest autos ever made Surprise! - Another Allyally, Elizea and lololol collab, need I say more? Beneath The Desert - One of the earliest, and most unfair riddle ever.