Hey folks! As we're passing the midway point for rating time, I've decided to compile some of my favorites among games I've seen this event. It's by no means comprehensive, as I've only played 30 games of the 2537 games this event. However, I think every title on this list deserves its spot, and I'll expect to see some of these games high up in the rankings come results day.
Without further ado, here are my favorite games so far, per category:
Fun

Timezone by @joemanaco (COMPO)
This fast-paced platformer is just an excellent game to play. You're forced to continuously kill enemies in order to survive, and the level design, visuals, and music are all excellent. There are only three levels, but they're each fairly long and difficult, so the full experience is really rewarding.
Innovation

Demonic Dealings by @paul-nadan (COMPO)
Is it poker? Is it guitar hero? Is it Pokemon? This think-quick playing-card-collection battle game mashes up a number of elements from different games into a surprisingly cohesive game jam experience. After the devil beats you in a hand of cards, your character is forced to gamble for the souls of others to repay his debt.
Theme

Pucamuc by @mors (JAM)
You play as a lopsided pink rectangle who crushes the life out of children in this punishing puzzle-platformer. Need to jump extra high? The cost is your own blood. It's a solid interpretation of the theme, in addition to having charming graphics and music.
Graphics

The 7 Cents Deal by @probe31 (JAM)
In this game, you play as a Catshier, giving change to the feline customers who frequent your shop. The game plays like a traditional cashier simulator with a twist, but the illustrations and animations have an incredible amount of scope and polish for a jam game.

Lousy Life Lessons by @awesomealliterationalliance (JAM)
Because the choice was so difficult, I included two games in my list for graphics. Lousy Life Lessons puts the player in the shoes of a cat stunt double, who slowly spends his nine lives in a series of increasingly dangerous stunt acts. The game integrates comic-esque illustrations and a voice-over narrative seamlessly into an action platformer where you have to always land on your feet.
Audio

Zugzwang by @riv-roy (JAM)
Looking at my graded games, I was a little surprised to see this at the top of my Audio list, because the game is so memorable for other reasons. It effectively plays like chess, from some alternate reality. You have five pieces with specific movement, and you get points when they die that you can use to cast special abilities to gain an advantage. In addition, the SFX are great and the music is haunting.
Honorable mentions for my audio spot include the aforementioned Timezone and Lousy Life Lessons.
Humor

Collecting Really Nice Cats! by @cheesepencil (COMPO)
You play as a disgruntled aging woman named Gertrude in this semi-physics-based cat lobbing simulator. You are tasked with literally herding cats while also avoiding young lads with baseball caps. The audio pushes it over the allegorical cliff of absurdity, and the combination of various cat noises, grunting, and voice acting makes it an overall great experience.
Mood

The Tenth Item in G4 by @daniel-alhadeff (COMPO)
This is probably the best game I've ever played featuring a sentient bag of raisins.
Conclusion
Not featured on this list, but still quite noteworthy, is utsvulten by @ditto. It doesn't fit nicely into any of the other categories because... uh... you just have to play it for yourself.
Also, all the jam games I've mentioned above definitely have multiple creators, although I've only linked the one that appears on the rating review page! Make sure to apply due credit when tossing the names and links of these great games around.
What great games have you played this Ludum Dare? Drop some of your favorites in the comments, and I might reevaluate my top picks.