The first Halo had staying bullet holes on the walls and bullet casings on the ground lingered for about five seconds. Halo 1 also had copious amounts of blood from dead players. Halo 2 through Halo: Reach have no bullet holes that I can remember and the casings disappear almost as fast as they exit your gun; they also have very little to no blood that I can recall. I would like to see the Halo 1 system return. Not caring so much about bullet holes/blood splatters on characters and vehicles, but it would be a nice touch.