Battlefield of the near future. Towable weapon's platform. Operator compartment on top, with dish antenna on top of that. Big generator in tow behind. Dish swivelling back and forth, slightly, making fine corrections.
Suddenly, a big roar as the generator spools up to a scream. Gout of black smoke pours out the stack, like when a big payloader floors it from a standing start.
In the distance, something bursts into flame.
(steely)
Take a conventional microwave oven, and open the door. On the inside of the door there is a diffraction screen made of black metal - using a set of snips or other cutter, remove a section of this screen (about a 2"x2" square). Shut the door, and take the oven outside. Place a glass of water about a foot away from the door in a direct line in front of the window, and turn on the microwave. The water will boil just as it would inside the microwave. Be careful about pointing it towards any plants or your lawn, as it kills plants almost immediately.
Always remember that microwaves bounce off of metal but go straight through glass. If you want to verify what this does to electronics, put a cheap transistor radio in front of it - it will fry - just like when you put a fork in the microwave (lots of sparks from the metal surface as electrons are freed). Directed into the grille of a car, the microwaves will find the electronic ignition, and kill the car. Into the passenger comaprtment, they will bounce around until they find electronics or meat (occupants) - so don't use it on the inside of a car.
All well and good until the other side figures out how to make a mirror(or corner reflector).