Turrets

Related:
* Hacking - hacking is occasionally possible for these.
* Robots - turrets are basically immobile robots, though shouldn't be considered part of them
* Auto-turrets - when attached to player's vehicle or character

Commonly these pop-up from some protective box like structures or similar to fire upon anyone they can find. Also commonly found as part of internal defence system of military bases, especially in science fiction.

This also includes manned turrets if the people manning it are an integral part of it (as in, they abandon it or otherwise leave it; often the people manning the turret are animated as part of it rather than individuals).

Occasionally these are indestructible.