Here's a great and theoretically realistic blood mod by PB&J for the Call of Duty 2 single-player campaigns.
Adds a more realistic blood effect to Call of Duty 2, along with splatter on walls and the ground.
To install, just drop the file PB&J_Blood into your "Main" folder (C:\Program Files\Activision\Call of Duty 2\Main)
load up either a new campaign or select a mission in mission select, and have a fun time.
Contact me at MDpirate@gmail.com