Your First Steam Purchase

Half-Life 2 back in december of release year was the first game i activated on steam from a retail disc :P
first digital game i bought was the first Left 4 Dead. :D

BioShock + BioShock 2 pack

Mount & Blade Collection

I haven't made any purchase on Steam, all the games that I have I got them trading and winning giveaways c:

Warhammer 40k DoW :)

First game on Steam? Half-Life Platinum Pack from a HL1 retail key.
First game bought on the steam store? Left 4 Dead.

Audiosurf. Then I didn't touch it for YEARS until someone gifted me Machinarium one fine Christmas. Then I barely touched it again until mid last year lol

Half-Life 2 Collectors Edition, though technically that was Retail and activated on Steam. It was the reason I installed Steam as it pretty much forced you to.

So Geometry Wars was my true first purchase on Steam.

12 Mar 2013 - Left 4 Dead 2 - $4.99 Purchase

Deus Ex:Human Revolution

The Binding of Isaac.

The first game that I ever bought from Steam itself was Neverwinter Nights 2: Platinum for $4.99, and I still haven't played it...

Dark Sector. mmm

half-life 2

the orange box, still my best purchase on steam :D

Terraria - 2011

Killing Floor :P

Half-Life 3.

Portal 2

Garry's Mod

GTA IV Complete

The binding of isaac :P

Garry's Mod + Counter-Strike: Source

First thing I owned: Borderlands (Gift)
First thing I bought: Garry's Mod + Team Fortress 2 (Bundle)

Actually my first purchase was humble origin bundle (not BTA). From the Steam itself using wallet i first bought TF2 backpaack extender which also granted me premium membership.