LEGO Portal™ Turret
Also known as the Aperture Science Sentry Turret™.
This MOC was based on the turrets in the Portal 2™ Level Pack for the game LEGO Dimensions™. I wanted to build that one, but I disliked how different it is from the turrets in the original Portal game. It had all sorts of gizmos on its back, and a weirdly short hind leg.
I went ahead and modified it to match the turrets in Portal. Removed the gizmos from the back and made it flat, carefully preserving the symmetry from a profile view. I also added a different kind of hind leg that is more faithful to the original.
You can download the building instructions from here: