6% of males and ~0.4% females have color blindness. A good number of games feature a colorblind mode (Forza 5 for instance). Many don't and have nearly unplayable sections as a result.
When I'm looking for a game, one of my greatest concerns is with color-coded information. If it exists, I need to see it in action, and if it's red-green or any other combination that is a problem, I need to know if I can change it. If I can't change it, I'll usually pass.

Some examples:
RTSs sometimes use red and green icons on minimaps - literally any other combination would be better. Homeworld Remastered's option changes (most but not all of) these to red and blue.
Forza's racing line originally changed from green (gas it!) through yellow (ease off) to red (brake) which is unusable and I'd switch to braking points only. Their option changes the green to teal.
Kingdoms of Amalur uses the common gold, purple, blue, green, and white rarity system for items, and managed to get purple and blue to look different by adding a slight bloom to purple, but screwed up gold and green.
Rocksmith (2011) used lime green, yellow and orange for three of the guitar string which can't be differentiated, and blue and purple for two more... they semi-fixed this for RS2014 by adding a colorblind mode and the results were a lot better, with cyan for lime, a darker orange, and rose for purple. It still wasn't great though, when compared to being able to customize string colors and pick something sensible like white or midtone grey to swap out for other strings.

Generally speaking, I'm used to scouring forums for info on colorblind options, but golly gee it'd be swell to have a database with that information, hint hint!
I'm sure myself and the other 96 million colorblind gamers would be grateful.

Games' ratings may be skewed or conflicting if they have wildly different ports.

For example, "The Legend of Spyro: A New Beginning" has its console ports, which are fundamentally the same, but it also has a 2D side-scroller port for GBA, and an isometric port for DS; both vary greatly (especially the GBA port) from the console release. Another example is Shrek 2, where the PC port is effectively an entirely different game from the console ports (and the matching PC port was called "Shrek 2: Team Action!")

Metacritic already separates game ratings by every port, and imo that's how it should be.

This one may look like a stretch, but there are many hardware-exclusive games out there, and it would be the same as the Arcade platform, which isn't, by itself, a concise hardware platform, but a concept.
The only handheld electronic game option on IGDB now is the Game & Watch, but there are many games, even in renowned franchises, for things like the Tiger Electronics and other smaller brands.
The one I got to know recently was the Nelsonic Game Watch series (don't confuse with Game & Watch), which had some games licensed by Nintendo itself, like The Legend of Zelda Game Watch and Super Mario Bros. Game Watch.

Wikipedia on this platform: https://en.m.wikipedia.org/wiki/Handheld_electronic_game

Several games have interesting or obscure caveats in terms of their release or their playability, and it's worth mentioning them for the sake of completeness. For example, Donkey Kong Junior is listed as a Gameboy Advance release, which is technically correct, but it was only playable via the e-Reader, which is not obvious. Additionally, Donkey Kong Junior also exists as a playable game within Game and Watch Gallery 3 and 4, which may technically not count as a release but deserves mentioning somewhere. There are several examples of games with unique scenarios like this, and this data doesn't really have a section where it could easily be integrated. Furthermore, some games have memes or cultural phenomena around them which also lacks a section. A trivia section to serve as a catch-all for data like this would be great, so long as said trivia can be cited and verified.