Dead or Alive Last Round I think is playable without Steam. It was half a year ago, but I had to do a reformat of one of my drives which basically wiped part of Steam out, but not the game. I remeber clicking on the exe as an experiment and the game started - No Steam there.

I just added the Linux version of Hollow Knight, and I'll be adding the others soon. Also, if we can get a confirmation on Dead or Alive, it'd be great to have another big-name title that's DRM-free.

Okay, we're updated again!

I assume you tested the Windows version?

I've tried Dead or Alive 5 before (and again just now) and I've never gotten either the startup_setting.exe or game.exe to work without Steam's presence.

Yeah. I only have Windows, so I can't verify that it's DRM-free on other operating systems.

I've started playing all my Steam games in Off-Line mode.

This seems too good to be true. Am I setting myself up for something awful?

I do not know if it is true, but some info said that Steam off-line mode is not permanent.
You have to login monthly or so.

I guess this could be helpful:
https://www.gog.com/forum/general/how_to_run_steam_games_offline_forever_tutorial

Does anyone know if age of empires or age of mythology or rise of nations from steam work without steam?

Generally speaking you'll just miss achievements and cards, if you care about those (you probably don't, I'm just saying). Other than that, there are games that might cut some features when you're not online (e.g. X3 Terran Conflict) or fail to validate DLC, but that's more game-dependant than steam-dependant.

It's supposed to last indefinitely, but it never worked that well for me. Back in 2011 it was a huge pain in the ass, had to relog at least once a week or so, but they improved it a lot over time. Now I can stay offline for months without issues.

Demon Peak

http://store.steampowered.com/app/525380/Demon_Peak/

A nice metroidvania game with snes graphics.

Tested on Win10Pro 64 bit

Don't forget to install OpenAL. Included in the folder.

Okay, I just added Demon Peak, Killer is Dead - Nightmare Edition, and Yonder: The Cloud Catcher Chronicles to the list!

Offline Mode used to require the occasional validation, but it doesn't anymore (see here: http://steamcommunity.com/discussions/forum/1/864969953572102601/#c864969953730401285); that was a bug that was fixed a few years ago. I myself have an Offline Mode client backup from over two years ago, and it still works perfectly, along with every backed-up game that was in my library at the time.

I've tested Life Goes On: Done to Death on Linux Mint and Windows 7 and on both of those systems, it seems to require Steam client running.

Otherwise, it seems that the jump button summons nothing when launched without Steam.

So, it launches without Steam but you can do nothing in game. Weird way to enforce Steam. Anyone else test this?

Each of the three games (or cases to be more precise) from the Sherlock Holmes Consulting Detective Collection will run without the Steam client on account of them using Adobe Air. Tested on Windows 10.

Why did you add Killer Is Dead? I could not see it posted here and I just tested it and it does not seem to start without steam.

Edit: I figured it out. You'll have to rename/delete steam.exe or create steam_appid.txt with 261110 in it and put it in the folder with the binary.