Milky Way Prince – The Vampire Star (https://store.steampowered.com/app/1302050/): Tested the Windows version. Already listed in the wiki, but it's listed wrong. From what I tested, you need to create a steam_appid.txt file in the same folder as "MILKY WAY PRINCE.exe" and add the game's ID (1302050) in the .txt file.

Tales of Beasteria (https://store.steampowered.com/app/1203030/): Tested the Windows version. Soon to be removed. Works right off the bat, no special setting up needed.

Detective Grimoire (https://store.steampowered.com/app/272600/): Tested the Linux version on Ubuntu. Also already listed in the wiki, but I think it's worth mentioning that, to get it running, I had to install two dependencies, libgtk2.0-0:i386 and Adobe AIR.
- To install libgtk2.0-0:i386, I had to run the command sudo apt install libgtk2.0-0:i386
- To install Adobe AIR, I had to run the command wget -O adobe-air_amd64.deb http://drive.noobslab.com/data/apps/AdobeAir/adobeair_2.6.0.2_amd64.deb then install the downloaded .deb package.
- About Adobe AIR, if you use a distro with a x86 architeture, you can probably get the .deb package from the command wget -O adobe-air_i386.deb http://drive.noobslab.com/data/apps/AdobeAir/adobeair_2.6.0.2_i386.deb

Not sure if anyone else has tried running this game without needing Steam, but it seems like YAIBA: Ninja Gaiden Z is DRM-free on Steam by launching the game directly from NRZGameLauncher.exe (not NRZGame.exe). The game came with a steam_appid.txt file containing its Steam App ID and I was able to play a couple of levels so far without being prompt to log into Steam.

Yes, but sadly it still needs Steam to run.

Does anyone know if sdk apps like Hammer can be run outside of steam? And what the experience is like if so?

Pode is DRM Free. Works straight from the .exe. No tricks needed and the save fie even seems to be cross compatible.

Windows 7

https://store.steampowered.com/app/944080/Pode/

Thanks for letting me know. I was hoping that Square would repeat the pattern they had with Final Fantasy X / X-2, FF12, Dragon Quest 11 S, and Trials of Mana, but I guess I should have known better.

Shattered Tale of the Forgotten King works DRM Free.
https://store.steampowered.com/app/1045180/Shattered__Tale_of_the_Forgotten_King/
Tested: 26.7.2021

Mail Mole works without Steam running. No special tricks needed and saves seem to be cross compatible.

Windows 7.

https://store.steampowered.com/app/1273540/Mail_Mole__Xpress_Deliveries/

Daymare: 1998 is DRM-free. I'll be updating the wiki soon.

Sorry for the slight off topic, but what about what I asked in the post #1665? (from July 8th, in case the link doesn't work)

I'd be willing to mention that in the wiki, sure. I don't know which ones have them and which ones don't, though. I was generally just sticking with what the Steam store page for each game says, but we could list the Linux versions.

I mentioned a few in my comments, but I'll sort them in a new comment when I get the chance so that it's more comprehensive and easier to get the information for the wiki.

Meanwhile, I tested some more games, and I tried listing the information in a more comprehensive way too. Hopefully it helped.

The games:

May’s Mysteries: The Secret of Dragonville (app/327650):
* Abstract: Runs kinda fine without Steam and appears to save fine.
* Long version: Can be run directly from the exe without using command arguments, removing dlls, adding extra files and such. The only special setting up needed is adjusting the computer's internal resolution if the game complains about "display not supported" (it wouldn't run on my virtual machine because of its smaller resolution).
* Additional information: Delisted game, and only available in Windows.

Grobda Remix (app/739000):
* Abstract: Runs kinda fine without Steam and appears to save fine.
* Long version: Can be run directly from the exe without using command arguments, removing dlls, adding extra files and such. The only special setting up needed appears to be to play it on Windowed mode and with a resolution that fits your screen, or else you won't be able to use the in-game options, such as the save button.
* Additional information: Getting delisted soon, and only available in Windows.

Both games tested on a Windows 10 virtual machine that never had Steam installed and on Ubuntu with Wine.
And while Ubuntu had Linux's native Steam installed, Steam doesn't seem to detect games running on Wine, and neither do the games on Wine seem to detect Linux's Steam even if it's running at the same time as the games.

Hedon is DRM free, according to the game's page and the dev on Twitter.

Game page: https://store.steampowered.com/app/1072150/Hedon/

From the store page: And with this wording, it also seems to be one of the few games on Steam that lets you keep the game in case something like Steam going "poof" happens.

And from Twitter:

There are many thousands, if not tens of thousands, of such games on Steam. Definitely not one of few.