I’ve only a couple game jams, but when it’s time to play test other people’s games, I try to go through the “needs ratings” categories, since everyone deserves some votes. The 5 big things I’ve seen missing from games,

No explanation of controls - I don’t need much “Space - Jump” is excellent, but some times people have like for interact, and there’s nothing calling it out.

A way to exit the game - I had 3 submissions in a row, that all had some variant of alt + f4 to restart and try again. I think 2 of them were in Unreal Engine, not sure what the 3rd was. It’s just good form to have a safe way to start, and exit.

Sound - Like any sound at all. It’s very ominious when there’s no music. I made some terrible stuff with Google’s Sound maker and then I used RaylibTech’s SFX generator for some noises. A game without sounds is unsettling, and bad sound is better than non, in my opinion.

Use .zip files - We can all argue about how great 7z and Winrar are (they are), but when I’m installing a game, every road block you put in my way, puts me closer to giving up. If I have to install some new tool, or deal with some side package (emulator, or special runtime) I’m probably not that interested.

Screenshots/gifs - I’m a big offender, but your itch page needs a screen shot or a gif (LICEcap, or screen2gif are great). If people know what to expect when it loads, they’ll feel more confident the got the right game, or aren’t being scammed.

So I was hoping to expand this list. Does anyone have any other “must haves” in game jam games?

As I have hosted a few of these jams now and have played every entry live I have to agree on these points. Especially being able to properly exit, it can be a real nuisance at times when I'm trying to manage the streaming software in a pinch but don't have an effective way of accessing it. 

Another point that's a little more personal for me, as someone who goes through every entry one that bothers me is when games are simply just called the name of the game jam. It can be difficult managing folders of games when some have near identical names. I know coming up with titles can be difficult but even if it's a descriptive title that describes the game in some way that would be better.