Forerunner automated turret
From Halopedia, the Halo wiki
The automated turret is a form of equipment so far only encountered on the Halo 3 levels The Covenant, Halo and The Ark. It seems completely safe to assume that it is Forerunner technology due to the fact that it resembles a stripped-down sentinel, and fires a thin, blue, sentinel-beam-like beam at enemies. Another fact to support this is the fact that when used against the Flood, its more effective than against the Covenant as it can instantly target and kill infection forms within seconds. However, due to programming issues, it has major problems picking out targets and more often follows allies with its targeting system, and does not fire. But the beam is extremely powerful and can kill a full armored brute in 2 shots. Also, if the turrets are not destroyed while/or after defeating Guilty Spark in the level Halo, they will attack you.
This piece of equipment is unavailable in custom games, matchmaking or even Forge. Template:Equipment List
