Neil Fraser, a software engineer at Google in California, has created a one of a kind Sentry Pumpkin paying homage to probably one of his favorite games, Portal. Neil says on his personal blog,

Perched precariously on its three legs, the turret automatically pans left and right and pitches up and down searching for targets. Inside is a small motor and a system of gears and cams to drive the gun mounts.

Construction was fun. Working on the mechanism within the pumpkin felt at times like building a ship in a bottle. A wet, slimy bottle. I can also confirm that the turret design is as impractical in real life as it looks in Portal, the guns have a limited field of view and the whole top-heavy contraption wants to tip over at the first opportunity. How the turrets deal with recoil from the gun I'll never know. This was clearly the work of a graphic designer, not an engineer.