I know what you mean. I've heard dozens of legends, I'm still trying to separate myth from fact in many of them.
One of my favorites was the "star tracker" used in the SR71. That plane, and its drone, used the same kinds of computer systems that were developed for Apollo (ref. "Skunk Works" by Ben Rich). There was a special gizmo to track stars for navigation, however, and there are some odd rumors that the computer in that used something like "perceptron" circuitry.
Another one I like is the one about the Navy SEAL goggles that use phased-array sonar to enable divers to see through muddy river water.
Also, what is the real direct destructive capability of military lasers? I've heard guys swear they saw one blow a truck into hand-sized pieces, but I wonder if there is confusion with laser-guided bombs and such, or intentional misinformation.