What was your first steam game?

Portal 2

Technically it was Hitman: Blood Money on this account (bought on June 9, 2010), but when I was waaaay younger I got Half Life 2 when it first came out, which required you to have a Steam account. I just never used it after that, until a few years ago when I created a new account.

Counter-Strike 1 Anthology.
but first buy from store was a "Garry's Mod + Counter-Strike: Source" bundle

Garry's mod and i still play it

Call of Duty Modern Warfare 2

portal 2

Counter Strike 1.6, fall of 2003, 4-digit Steam ID. ;) First non-valve game was Rag Doll Kung Fu!

TF2

Half-Life Platinum Pack

terria

Chime.

Bastion

The Orange Box.

Warband.

King's Bounty: Platinum

css + hl2 deatmatch + dods pack

Left 4 Dead 2

Half-Life 2

Physical Orange Box.

CS 1.6, but on current account box version of COD MW3.

First game was Portal when it was handed out for free then my first bought game was Left 4 Dead 2.

I thought there would be more HL2 answers in this XD
Well for me it was atleast

F.E.A.R 3

Counter-Strike: Source.
Though it suddenly disappeared. :/