According to a coworker of mine, a physicist has a device the size of a small car, which holds some ten trillion positrons in containment, and has a wand attachment that can fire them. Positrons, are, of course, anti-electrons, and annihilate electrons on contact, producing a burst of energy, usually heat, light, or sound. (Although sometimes you only get neutrinos out of it.) So when fired, this produces a little beam of light from annihilating the air that it touches, and a strange sucking sound as air rushes in to fill the vacuum.
He then pointed out that technology tends to, over time, cheapen and miniaturize. This machine might be the size of a car and cost more than the entire neighborhood that I live in, but one hundred years from now it'll probably be the size of a flashlight, and be purchasable for a few of whatever they use as currency then in a corner store. It would be useful as a cutting tool, as it would make a tiny part of anything you touched to it literally cease to exist.
So in short, this machine is the precursor of George Lucas's lightsabers. With one major distinction. Lucas's lightsabers could be stopped by each other. This thing's beams would go right through each other if you had more than one.
This would not be the first time that science fiction inspired a real world invention. Plasma shields existed in various sci-fi productions for years before NASA built a real one to deal with the real problem of space dust. (Because collisions with even tiny chunks of dust are a problem when they occur at hundreds of thousands of miles per hour.)