Like this page on Facebook and you'll get a code to a free, fully legit copy of Metro 2033.
You can also add this game to your Steam account if you want to.
When you 'Like' their page they send you to a page that shows you a game code. You can copy this code into Steam and have a free copy of Metro 2033 added to your Steam account. Just go to the Games menu in Steam and then 'Activate a Product on Steam....', where it'll ask you to enter a code. Very nice if you prefer your games to come through Steam.
You have until Dec 16 to do this.
Not sure if this has been posted yet, and I'm too lazy to search. if it has, I'm sorry.
Gah, I see it's already been posted in the game sale PSA. Mods, feel free to delete this thread if you wish.