6. Soldier of Fortune II: Double Helix - Activision, 2003 - PC, Xbox
This one's a case of delayed gratification. Soldier of Fortune II: Double Helix was... "celebrated"... for its dismemberment system - players could slice off limbs, even faces. That was particularly brutal, even as recently as 2003, but realistically, the blood didn't spray - it oozed.
Slowly, deliberately, once the body of your enemy had slumped over as a pile of literally dead meat, blood trickled out, pooling under the corpse and spreading across the floor. Many games go over the top with depictions of blood, but Soldier of Fortune II kept it subtle and sick.
Above: Soldier of Fortune II: Double Helix: keeping alive the grand tradition of horrifyingly inhumane corpse mutilation.