Battle, by 
Just reading the name "Blood Libel" and the tagline "This level is fundamentally Sisyphean" felt like taking two verbal punches in the face, and the level itself lives up to them.
I love when levels try weird gimmicks, and I found these gimmicks play pretty well! The layout delivers the feeling of Getting Over It With Violet CLM without having awkward flow, and I died plenty despite the presence of an almost-instantly-regenerating full carrot.
The duo bouncers are a great idea, I've played a lot of levels with both regular and upside-down bouncers and every single one of those levels should use these instead. Also I like how the ammo sprites remind me of particle physics.
I'm less impressed with the bird and the moving platforms – using the platforms feels a bit too slow and precise for multiplayer. And I'm sure there's some cute stuff you can do with the bird, but with the duo bouncers already letting you attack people above you, it mostly just feels like a shield.
This level's visuals are downright surreal compared to the other contest entries', and it's all the better for it. Of course there's the superb custom palette and the very very bright red moon/sun/whatever (ooh, ALPHAMAP!), but I also adore the smaller details like the guts-colored sky growing closer as you ascend, and the water splash animation being recolored.
It's also excellent with landmarks, every spot looks unique and the layout was really quick to learn.
I do think literally raining blood might be a bit too on the nose, but it does look good.
Overall, this is for sure the most original entry and my personal favorite, I'd be delighted to lose to it!