Manhunt was fascinatingly macabre at times and the snuff premise was suitably disturbing. Still one of the most atmospheric games I know.
The stealth kills were nasty even at white, while red kills bordered on the fetishistic. Not to mention the mess a pointblank shotgun blast to the face made. The sickle is always everyone's favorite weapon (though I preferred the baseball bat) and while the red kill was suitably nasty (grabbing a guy's head from behind and cutting his gut open), the yellow kill takes the crown for whince inducing. If you haven't played it, Cash sneaks up to a hunter from behind and swings the sickle up into their crotch, before pulling it back horizontally.
I thought Resident Evil 4 was brilliantly macabre, especially the shotgun. Later on in the Mercenaries minigame, Hunk's closerange neck snap and Crauser's arm attack provided further dark hilarity.
I also still remember how dark and freaky the original Prince of Persia felt because of the surreal traps and violence towards the main protagonist. Those cutters still give me the chills, even though it was admittedly fun pushing enemy guards into them or off ledges into pits of spikes.
I personally wasn't too impressed with the damage modeling in Soldier of Fortune 2. The collision detection felt ridiculously random and while apparent attention to detail had been paid to damage on the head, the rest of the body seemed like an after thought. Shooting someone with a pistol in the arm made a hole. Shooting a second time removed the hand. Shooting a third time removed the entire arm. That, and the pool of blood that was left behind when the body disappeared (lol?) looked like molasses instead of blood.
Jam it back in, in the dark.