Turrets are part of the Engineer abilities set, and can be constructed and placed on the battlefield. They autonomously scan the immediate area in an arc, and upon seeing an enemy combatant, fire at will. Turrets can be upgraded to be more powerful and more difficult to destroy, the earliest available form being about equivalent to the firepower of an SMG, with the second and third incarnations resembling an assault rifle then heavy machine gun, respectively.
While turrets can be deadly, they function more as a distraction, due to their somewhat limited scanning range and speed. Light body type players will be able to outrun or avoid their line of sight if they time it correctly.