Two from Doom 3:
The one where you walk into the room and there's a vivisected fat guy hanging screaming from the ceiling, attached by his arms and legs. His stomach is all ripped open and the skin is pulled out so that you can see the insides all hanging there. That one managed to get a bit of a reaction out of me.
Second, the one where you come across the only woman in the entire game. You walk up to her, she begs you for help, and then one of the ghostly floating skull things leaps into her and her head and spinal cord tear out of the rest of her body and starts flying at you screaming.
The one where you walk into the room and there's a vivisected fat guy hanging screaming from the ceiling, attached by his arms and legs. His stomach is all ripped open and the skin is pulled out so that you can see the insides all hanging there. That one managed to get a bit of a reaction out of me.
Second, the one where you come across the only woman in the entire game. You walk up to her, she begs you for help, and then one of the ghostly floating skull things leaps into her and her head and spinal cord tear out of the rest of her body and starts flying at you screaming.