[Iron Munro]

Build two walls, say 100 yards apart, and make the space between them a free fire zone for any US citizen doing target practice.

I've always had a liking for the Remote Sentry Guns as seen in the movie "ALIENS".

[Spirochete]

I've always had a liking for the Remote Sentry Guns as seen in the movie "ALIENS".

This device now exists on the Korean DMZ: the Samsung SGR-A1. It requires human permission to fire only because of the squeamishness of liberal generals regarding autonomous sentries.