Counter Strike: Source - 4825 MB
Half-Life 2 - 4762 MB
Half-Life 2: Episode 1 - 5935 MB
Half-Life 2: Episode 2 - 8580 MB
Left 4 Dead - 5557 MB
Left 4 Dead 2 - 7850 MB
Portal - 5054 MB
Portal 2 - 11200 MB
Team Fortress 2 - 10496 MB

EDIT:

Half-Life 2: Lost Coast - 2958 MB

Half-Life 2: Lost Coast is probably the smallest, given that it's really just a tech demo, and thus has very little actual content.

According to my Steam client, it weighs in at 2958MB of local files, but looking at the Steam directories, most of that seems to come from the engine itself and shared assets. Lost Coast itself seems to be about 300MB.

It's not directly available from the store, but if you have a proper graphics card (that is, ATI or NVIDIA), there are links to get it (and Half-Life 2: Deathmatch, which shows as 3844MB) on the Steam forums. I don't know if it actually checks your hardware, so maybe you can just use the links over there regardless. If you have an NVIDIA card, you also get the Portal: First Slice demo, which might weigh in at less than either of these.

What's funny is that they've been porting all Left 4 Dead content over to Left 4 Dead 2, and since they don't use the old GCF archive format, they're just wasting your hard drive space with twice the data.

?

how ancient is your harddrive for you to care about few gigabytes?

Couldn't you just buy an external HDD to store all of your non-essential files and to grant you with more room for expansion?

Ok, Lost Coast seems to be my best bet - I just hope my old computer has a new enough card! Would a Mobility Radeon 9600 get me HL2: Lost Coast? Ah, very old - I only have 9gb free, so that is why I am looking for the smallest option - and I only have HL2 - Ep1 and Portal for now. Well, I have got one, but it is nearly full too, plus then I would have to go messing around with my Steam directory and so on.

Just to let you know, the Steam directory is highly mobile. You can move the folder to just about anything. If there's a problem, you just delete everything in it except for Steam.exe and your steamapps folder, double click Steam.exe and it reinstalls very quickly.

It does have a habit of resetting your categories if you've got them sorted out though.

Ok, I will have a look around and see if it will run by itself - and thank you for the kind offer, I will let you know what turns out.

EDIT: Yes, by the looks of it, you can download it (3GB) and it will run by itself - or, if you have a Source game installed, then it is 150mb.

The Steam page for it says that you need 150mb HD space, yet when I go to download it in Steam client, it says 3GB.

If I am wrong, please correct me.

Day of Defeat source is the smallest game at only 1882MB. I'm surprised no one mentioned this game earlier. I just bought it yesterday in a steam sale to add to my Source games collection.

Be aware that Garry's Mod has been known to download additional Source game files when it decides it needs them. So if you see other source based games showing up as installed or as download paused, that's why.

Damn! I didn't even know DoD what Source. The sale has ended now, unfortunately.. if it was still going then that would have been perfect - not only because of size, but it has all those WW2 weapons, of which I would be interested in having in Gmod

Is there no way to stop it? I would prefer to have just one game Gmodded, thank you very much Garry.

DOD: Source is listed as 4424MB of local files here. I suspect those 1882 MB are actually excluding the Source engine - which, if that number comes from the install dialog, makes sense if you already had a Source game installed (e.g. TF2).

Yes, it worked!

Thanks guys, but this is the 'solution,


But thank you all the same for your suggestions!