Just going by this:

http://www.gog.com/forum/general/list_of_drmfree_games_on_steam/post424

I just noticed that it seems like a lot of the Half-Life games got updates just over a month ago, so I'm wondering if that's when the dependency upon Steam was removed. If you log into Steam, the update info is in the news section of each game's page in the library.

Just tried Brothers: A Tale of Two Sons and it seems to run fine, moved folder, uninstalled from Steam and launched the Brothers.exe file. Fine so far no problems but played for just a couple of minutes, not all the way through since I did this,

2 more, Antichamber and Sang-Froid Tales of Werewolves both seem to run fine too, moved folders, uninstalled from Steam and launched the .exe

Bionic Dues by Arcen can run without steam.

Running without launching Steam or on a PC without Steam? Also, which OS do you use?

I added Brothers and Sang-Froid, hopefully your information is valid.
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List of DRM-free games on Steam

Sorry for the lack of details, I ran out of time this morning.

So, to be more precise, Bionic Dues needs Steam to install and update the game, but you can copy BD's folder and run it independently on all OS. That's how the dev intended. And I use windows.

Splinter Cell Chaos Theory (Multiplayer/Versus) is DRM-free. Just tested myself, no Steam required.

This cool idea :)

Got another one which excites the hell out of me: Batman: Arkham Asylum Game of the Year Edition.

Go to the Binaries folder and create a shortcut to ShippingPC-BmGame.exe, and add " -nosteam" (without quotes) at the end of the Target field. If you run the game like this, your save data will be completely separate (and non-interchangeable) from any save data you have by playing the game through Steam. The non-Steam save folder is located in Documents\Square Enix.

I was just messing with random commands that could possibly disable Steam, and lo and behold, -nosteam worked great.I can only imagine that this happened because of the recent switch from Games for Windows - LIVE to Steam that the Arkham games went through; the same trick doesn't work with Arkham City, unfortunately.

I thought the Batman games have GfWL that you can't disable - but i don't own them so I can't say for sure.
My question was "how do you figure all that commandline parameters out?" - okay, guessing :)
Still awesome found.

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List of DRM-free games on Steam

GfWL is dying, and have been patched out of the Batman games on Steam.

Yup, GFWL is pretty much dead now, so no need to worry about that. Save data for this game in particular still seems to be somewhat encrypted, though.

And heh, yeah, it was literally just a command line guess. :P I remembered seeing something saying "nosteam" in some Humble versions of games, since they were Steam-only until Bundles came out, and then they were made DRM-free. I just tried that, and it happened to work.

I played a bit around and found a couple of games:

- Dysfunctional Systems: Works under Linux but not Windows
- Cherry Tree High Comedy Club: Works fine
- TrackMania Nations Forever: Works fine
- TrackMania² Stadium: Doesn't launch Steam if Steam cannot be found
- TrackMania² Canyon: See Stadium
- Sanctum: Works fine
(- Sanctum 2: Launches without Steam, but input does not work so playing the game is not possible :( This could be a technical issue I haven't solved yet. Maybe there are incompatibilities from 32bit/64bit)

Notes for the ManiaPlanet (below: MP) games (this excludes Nations Forever):
The games must be installed an played once through Steam before they can be played without Stea. Otherwise there will be an error in MP that says that the games can't be found.
If you own more than one MP game, you only can play the game which .exe had been ran though all other games are displayed in MP.
The games can be played offline, but there won't be the singleplayer campaign and no ranks/ladder. However the campaign can be played a bit circuitous by playing the maps in a local game.

TrackMania² Valley and ShootMania Storm should be the same - the demos did work.
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List of DRM-free games on Steam