If you’ve never played through Eidos’ brilliant sci-fi RPG Deus Ex games, you now have absolutely no excuse, because you can pick up both Deus Ex: Game of the Year Edition and Deus Ex: Invisible War on Steam for just $5; it’s normally $20.
The sale is listed as a “mid-week” deal, so get to it. It won’t last much longer. And if you need any more reason, think of it as necessary research to prepare you for Deus Ex: Human Revolution. You don't want to be completely in the dark, do you?