Laser technology has led to the development of a replica Star Trek phaser that actually works.
Laser Pointer Forum member Jayrob has created a fully working Star Trek phaser replica that is powerful enough to easily pop balloons. He uses a Kirk-era phaser, giving it an old-school charm, and it even makes the proper sounds.
Judging by the video, it appears to be a Type-II Hand Phaser from the year 2266, but I wouldn't know off the top of my head because I'm more of a Next Generation man myself. Jayrob created a phaser in the past that used a green beam, but it's not as powerful as this one due to some sort of new custom focus adapter.
Jayrob isn't the stingy type that wants to keep the secrets of his phaser all to himself, he's written complete tutorials (found through the earlier forum links) and even offers help getting some of the parts. The Escapist also showed you how to make a phaser last year, but Jayrob's is amplified and looks even scarier. If you do take it upon yourself to build a phaser, just make sure you get proper eye protection. These phasers won't stun with a single shot or completely evaporate human beings into dust like they should, but the human eyeball won't come out unscathed if it takes a hit. I hereby request that someone make a Next Generation version.