THQ have a deal/promotion on until the 16th of December where, as stated in the title Metro 2033 is entirely free.
Not sure if you guys already own it but if you don't now's a great change to try it.
!!!WARNING!!! you require a Facebook Profile if you really dislike Facebook you could always make a fake account :)
Goto www.freemetrogame.com (http://www.freemetrogame.com)
It is a Redirect to Facebook so Like Them, Simple ;)
Spoiler
(http://i.imgur.com/j7whD.png) (http://imgur.com/j7whD)
MOAR proof/Info
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(http://i.imgur.com/ntL4O.png) (http://imgur.com/ntL4O)
Final Evidence it Does work i already own the game though ;)
For you To lazy to Facebook.
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(http://i.imgur.com/PWFaB.png) (http://imgur.com/PWFaB)