Spec Ops: The Line. If anyone here ever wanted to play a genuinely dark game, then this it.
I bought it because it's set in ruined, dead Dubai, and I wanted to see how that looked.
Early on, I shot a deer and got an achievement. I lol'ed.
That was, quite literally, the last time I laughed in the entire game.
I can't give too much away, lest I spoil it for those who want to play it, but it delves really deeply into the concepts of good and evil, the darkness that hides in the heart of every human (thank you, Heart of Darkness!) and, most importantly, the concept of being the hero. Battlefield, Modern Warfare et al give you an achievement for massacring 700 brown-skinned terrorists and disarming a nuke; this game tries to how you that sometimes, being the hero can lead to horrific, horrific outcomes. Even if you only ever had good intentions.
It's not a funny game, or even a feel-good game. But, if you guys want to play something more philosophical, and more introspective, then this is the game to beat. Great story, great writing, and completely worth it if you've got a few hours to spare on a weekend.
However, it is absolutely not recommended if you just want to shoot some dudes on a hung-over Saturday morning like I did. It will make you weep, I kid you not.