There are some fascinating things you could do with one of those. You could, for example, make a "stick boiler"—like a "stick blender"—that you stick inside a cup of liquid to heat it up, without any part of the stick itself getting hot. (Presumably there'd be a waffle-grid cross-guard to block reflected RF.)

But, in the wrong hands, that's a directed-energy weapon, isn't it? (Hell, stick one of these in the right kind of tube and you've now got a coherent RF beam—a maser pointer. You could probably burn your name into a wooden building from across a football field with one.)

You can do plenty of damage with a normal microwave oven in the wrong hands, I remember reading a book from the library a few years back that detailed making an EMP from one.

Thinking of that book, I don't think it's likely that libraries would carry that kind of book any more, sadly.

Which book was that? A portable EMP could be really useful....

If I remember correctly, I think it was this one

http://www.amazon.com/Build-Laser-Phaser-Working-Projects/dp...