Deus Ex: Human Revolution.
Discuss (remember the spoiler tags if necessary! Don't spoil the game for those who haven't finished at least one playthrough yet).

I'm on my second playthrough and planning my third. It's a fantastic game. Great length, and great variety to how you play.

On my second playthrough I was walking through a room all casual-like because I'd found a pass-card that gave me authorization to be there. At the same time, my brother was on his computer behind me in the same room, trying to live long enough under a barrage of bullets to kill everyone and clear his path. On my first playthrough I didn't find a pass-card, and sneaked my way through the room. The freedom to pass the game with different play styles and different paths is fantastic.

Jibb