This is the sort of thing that should really be more expensive, just so people think twice before getting one. Wicked Lasers' Spyder III Pro Arctic Series is a laser device that costs only $200, that can light things on fire. It uses a ~1-watt blue laser diode harvested from a home theater projector to produce a 445nm beam that can burn, blind, and generally cause havoc.
To put it in perspective, the average laser pointer is around 5 mW, or 1/200th the strength of the Spyder III. At about 50 mW, a laser can be powerful enough to pop balloons from a distance. Wicked Lasers notes that the Spyder III is a Class 4 laser product (the most powerful commercially available laser) that can instantly set skin on fire and ruin eyes, and the company requires anyone who purchases a Spyder III Pro to fill out a waiver.
explored the underlying technology of lightsabers as described in various Star Wars media: a device in which a special crystal channels energy from a multi-megawatt diatium power cell into a blade of incredibly hot plasma. Ignoring the various science fiction concepts like special crystals and currently-impossible power sources, lightsabers can't work because of one simple engineering problem: plasma cannot be manipulated in such a way.
On the bright side, you can just drop $200 and get a hand-held laser that can burn things. Take consolation in that.