A real-life light saber?

Sounds more like a Star Trek phaser set on stun, to me:

The LED Incapacitator works by emitting a strobe of ultra-bright, multicolored, pulsing light. Once pointed at an individual, the built in range finder measures the distance to the nearest set of eyes and then adjusts the level, output and frequency of this beam, to unleash an optimal and continuously changing pulse. This results in giving the eyes and the brain no time to adapt, and whilst temporarily blinding the subject, it also causes a disorientating effect. Hence, the subject is overwhelmed by the strobe both physiologically and psychophysically. Inventors of the LED Incapacitator, Bob Lieberman and Vladimir Rubtsov, say that the effect of having the light shone into your eyes wears off within a few minutes. They are reportedly taking great care to make sure the strength and duration of the strobe falls within all safety guidelines for the eyes. “There’s one wavelength that gets everybody,” says Lieberman. “Vlad calls it the evil color.”