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. Evidence to further support this include that it's very effective when used against the Flood, much more so than when used against the Covenant as it instantly targets and kills Flood Infection forms within seconds, even when they are your allies.
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. The beam however is extremely powerful and can kill a full armored brute in 2 shots. Also, if the turrets were not destroyed after defeating 343 Guilty Spark in the level Halo, they will attack you, taking out your shields fully in Normal difficulty or killing you in one shot in Heroic and higher difficulty.
This piece of equipment is unavailable in custom games, matchmaking or even Forge. Template:Equipment List
