Forerunner automated turret

The Automated Turret is a form of equipment that acts as an automatic defense system for the player and first featured in Halo 3. It is so far only encountered on the Halo 3 levels The Ark, The Covenant, and Halo.

Function
This small robotic turret is Forerunner technology found on the Ark and resembles a stripped down Sentinel. It fires a thin, blue beam at enemies. This device is extremely adept at targeting and destroying Flood of all kinds, although it can be used to kill Covenant forces as well. It is extremely powerful and will kill a fully-armored brute in two shots. Technically it can be considered as a type of Sentinel.

Its HUD symbol is a silhouette of the contraption itself and vaguely resembles the symbol for the Power Drain.

Disadvantages
Due to programming issues, the turret has major problems picking out targets and more often follows allies with its targeting system, and does not fire and can not be found in forge or mutiplayer.

Also, after defeating 343 Guilty Spark and leaving the control room in the level Halo, any pre-activated Turrets will fire upon you (fitting in with the other Sentinels, who also attack). A turret activated after the fight with 343 Guilty Spark will attack the player and will turn your reticule red as it were an enemy.

Trivia

 * This piece of equipment is unavailable in custom games, matchmaking or Forge.
 * If these turrets are deployed before the destruction of 343 Guilty Spark in the level Halo and survive, they will attack you, taking out the player's shields on Normal difficulty or killing the player in one shot on Heroic and higher difficulty.
 * On The Covenant, during the part where the Flood ally with you, the turret will shoot at the Flood and vice-versa.