Bloody UNSC Marine
From Halopedia, the Halo wiki
An Easter egg found in the Halo 2 level Cairo Station. Play this level on the normal setting; it only works on this for an unknown reason. When you reach the loading hangar where you must defeat the first Covenant boarding party, ensure that you save the lives of all the Marines with you. When every last Covenant is dead look at your accompanying marines faces. One, in this room, will be cut, bruised and covered in blood. This is the only place in Halo 2 where such a damaged marine can be found.
Occasionally you can see a bloody marine on the easy setting, too.
These Marines seem to have less health than the other Marines, but this has not been confirmed; on any level above Normal, they seem to be normally one of the first to die. One is voiced by John Kassir. He also is one of the few Marines that never wears a cover (headgear) during the level (most other covers are the Dress hat, Sergeant Hat, or no hat). His overall accuracy (including grenades and rifle fire) is the same as a normal Marine. He also appears to have no pouches on his breastplate.
