Same PC, but recently copied from an old Windows installation. WIll try an integrity check in a sec.

For now:

Aztaka
Blocks That Matter
Legend of Grimrock
Nimbus

Edit: Was indeed a dodgy installation of ARES. Works fine now. Looks like the devs botched the implementation of the copy protection and forgot to have the program terminate when the message appears.

Have you even bothered reading the OP?

Just here to say, thumbs up gentlemen! This will probably be a useful list for me at some point in the future.

Dungeon Defenders probably belongs on the list. It's a weird case - you can switch Steam integration on or off, and when it's off you don't need Steam at all. When it's on you need Steam running to launch the game.

Yes, that's exactly what this thread is about.

How exactly do you do that? (I don't have the game, so I don't know what explanation to provide in the list.)

Tested these, all use Steam DRM:
bit.trip beat
world of goo
rush
Doc Clock - The Toasted Sandwich of Time
ion assault
sonic generations

They either start Steam or fail to start with a message that steams not running

I will check some of the AAA titles a bit later on, have a fair few installed but I have a funny feeling they will start the client up

I had a few AAA titles on this system which I tested, they all came up blank. Not sure where you would place Mini Ninjas (the other Sqeenix games tested (3 other) did not), Dungeon Siege 2 (1 and 3 did not), Strangers Wrath and Psychonauts (Stacking and CQ did not). May just be carelessness and they forgot to implement it? (and because of this thread they are now becoming aware of it and it will be patched in next week)

I can make a list of the AAA games i have tested. 2 secs

You can put Majesty HD and Majesty 2 Collection on the list, both work fine.

Then maybe it might be a good idea to put in your list an asterisk or any symbol to differentiate those that were tested with the basic "start without Steam" and those tested with the whole "copy to another steam-less offline computer" as I suspect there will probably be several false positive among the former.

W00t, I can add one

A Virus Named Tom!

Games tested which required steam client running:

1701 AD
Alice: Madness returns
Amnesia
And yet it moves
Aquaria
Assassins Creed 1 & 2
Auditorium
Avernum 4-6
bit.trip runner
Borderlands
Braid
Brainpipe
Cave Story+
CivCity Rome
Costume Quest
CreaVures
Dark Messiah of Might and Magic
Dead Space 1&2
Defence grid
Deus Ex :HR
Diamond Dan
Divinity II - Dragon Knight Saga
Dungeon Siege 1&3
Eets
E.y.e.: Divine Supremacy
Fallout NV
Fate of the world
Fear 1&2
Fortix 2
GTA: San Andreas
Greed: Black Border
Gundeadligne
Gundemonium recollection
Hamilton's great adventure
Half-life 2 (+ep 1&2)
Hitogata Happa
Hydrophobia
Just Cause 2
Lara Croft and the guardian of light
Limbo
Magica
Mirror's edge
Orc's must die
Plants vs zombies
Roboblitz
Runespell: Overture
Sanctum
Sequence
Sideways: New York
Sin 1 & 2
Skyrim
Space Giraffe
Space pirates and zombies
Spacechem
Stacking
Stalker CoP & SoC
Swords and Soldiers
Terraria
The Ball
The Baconing
The Ship
Titan Attacks
Titan Quest (+ IT)
Tomb Raider: Anniversary
Trine 2
Twin Sector
Two Worlds II
Uplink
Vampires the masquerade: Bloodlines
Xotic
Your doodles are bugged!
Zombie shooter 1+2

I may be able to test some more when I get out of the firewall I am behind now.

Sure, I can do that, but I currently do not have easy access to any computer that would fit the description. If anyone can provide this data, I'll be happy to mark such games in the list somehow. There's no rush.

For a list that's some 4 hours old, what we have now is not too shabby.

You can add Darksiders II and Prototype 2 to this list.