Next time you demonstrate in front of a G8 summit, you might feel a bit hot. The US Army demonstrated the Silent Guardian developed by Raytheon that uses an invisible energy beam (millimeter wave technology) to control crowds.

Raytheon calls the Silent Guardian a "Less-than-Lethal Directed Energy Protection".
Less-than-lethal sounds great. I like this term - makes me feel save.

The weapon’s antenna emits a focused beam of millimeter wave energy. The beam gets under your skin to a depth of 1/64 of an inch, producing an intolerable heating sensation. Raytheon says your reaction will be to instinctively flee or take cover. Raytheon also writes in the Silent Guardian data sheet: "The system is available now and ready for action."
More details on the Raytheon Silent Guardian page.