River City Ransom Underground can launch without the Steam client. At least, that's what the developer claims:
http://steamcommunity.com/app/422810/discussions/0/1458455461472121812/#c1458455461472187571

Well The Long Dark launches and has always launched without the Steam client

Just bought DOOM 3 and it does not seem to run without steam on my win 7. Still it is on the list. Did they change somethig?

This site is useful for such information.
http://steam.wikia.com/wiki/List_of_DRM-free_games

-Tastymonkey

Doom 3 is under the "Patchable Games" section. I assume it needs the latest patch (which removed the DRM from the retail versions), or should it fail, you can also use a source port like dhewm3:
https://github.com/dhewm/dhewm3/releases/tag/1.4.1

Ahem

pedrovay2003 maintains that list with input from this thread.

Will try this and report back. Thank you, Grargar.

Edit: Used the executable of the latest retail patch (same version # as steam) and it removed the DRM. Thank you again.

Conquest of Elysium 4

http://store.steampowered.com/app/403950/Conquest_of_Elysium_4/

Dominions 4

http://store.steampowered.com/app/259060/Dominions_4_Thrones_of_Ascension/

Rogue's Tale

http://store.steampowered.com/app/265990/Rogues_Tale/

All Hegemony serie

http://store.steampowered.com/app/202690/Hegemony_Gold_Wars_of_Ancient_Greece/

http://store.steampowered.com/app/227060/Hegemony_Rome_The_Rise_of_Caesar/

http://store.steampowered.com/app/308173/Hegemony_III_Clash_of_the_Ancients/

Horizon

http://store.steampowered.com/app/236130/Horizon/

Infinite Space serie

http://store.steampowered.com/app/226120/Weird_Worlds_Return_to_Infinite_Space/

http://store.steampowered.com/app/269990/Infinite_Space_III_Sea_of_Stars/


Tested on Win7-32, should run on everything (within the confines of related system requirements).

Brigador: Up-Armored Edition works fine without the Steam client. Tested on Windows 10.

I've got four new entries to add as working on Linux:

DEADBOLT
Interplanetary
Jazzpunk
Massive Chalice

And three others that can get a check mark added for Linux:

Agatha Christie - The ABC Murders
Ninja Pizza Girl
Stardew Valley

Life Goes On: Done to Death seems to be botched on Linux (and Windows). I think it should be off the list because it's unplayable without Steam.

Some more games for the list:

SEUM: Speedrunners from Hell (Rename Steam.exe or create a steam_appid.txt file with 457210 in it and place it in the same directory as the game's main executable.)
Shadowgate: MacVenture Series
Shadowgate (2014) (Rename Steam.exe or remove steam_api.dll)

All tested on Windows 10.

Hey everyone, thanks for working to put this list together. I recently used it to figure out what I had that was DRM-Free, and here are some of my findings:

I don't trust myself to edit the wiki without breaking all the formatting, so I haven't updated it with these:

DRM Free (Windows 10 x64):
---------------------------------------
Deadbolt (remove steam_api.dll)
Electronic Super Joy
Faerie Solitaire
Gunman Clive
Journey Down, The (Chapter Two)
Okhlos: Omega
ROD - Revolt of Defense
Thirty Flights of Loving

Games the Wiki says are DRM Free but I couldn't run (Win 10 x64):
----------------------------------------
DCS: Blackshark
Machinarium
Misadventures of P.B. Winterbottom, The
Rock of Ages
Wasteland 1 - The Original Classic

Maybe some of the above require renaming/removing Steam? Could very well be my fault or unclear instructions; not trying to say they're for sure broken.


Miscellaneous Notes:
---------------------------------------
For Unreal Tournament 2004 (after v3369 patching) I had to use regedit to write my legitimate CD Key directly into the registry. After that, it quit complaining and launched fine.

Although the Space Quest Collection launcher does include CEG (I have to run the individual games), the King's Quest Collection launcher does not -- I could run it from SierraLauncher.exe with no problems.

Although probably outside the scope of this topic, I couldn't get Fallout 3 to run on Windows 10 with any combination of FOSE, the 4GB LAA patch, FOMM, and the GFWL Remover.

Machinarium got rid of Adobe Air with some of th elatest updates. That might be the reason for it not longer being DRM-free on steam.