Your First Steam Game

Portal was the first game I activated on Steam. I still have the retail box somewhere.

Portal for free :P

CoD 4: Modern Warfare

Terraria & VVVVVV :3

Terraria was the first paid i bought, but TF2 was the first i downloaded.

The Orange Box. Epic bundle, best buy I ever did...

CS 1.6

I believe I registered for Steam after purchasing and getting keys for the first Humble Indie Bundle, I figured it'd be easier to download and install the games like that. Half a year or so after that, I built my first actual 'modern gaming'-capable PC and started buying games via Steam..

Half Life 2

Audiosurf

Audiosurf + TF2.

For me it was Half Life Generation Pack

MW2 (is i know cod is lame)

I'm sure most people will say Half Life or something, but mine was Sniper Elite.

Skyrim <3

left 4 dead

Portal 2. I had bought a physical copy, and got the original Portal with it! :D

Half Life Platinium (HL 1, CS 1.6, DoD, etc.)

Portal.

CS 1.6 and HL1

Titan Quest Gold

counter strike source

tf2

my first steam game was F.E.A.R.2 because its steamworks. followed by the orange box

mine was tf2 (i just created my account to get that game =D )