Deus Ex: Human Revolution. I'm on my 3rd play-through now, and I've barely played any of my other beloved games while I've had it.
It really fits my negative, slightly dystopic, view of the future, and the gameplay is right up my alley, despite a few flaws.
Best 7£ I ever spent.
I'm planning on playing Mass Effect and Fallout 3 when I'm "done" with HR...