Kipkay bought a model of the Star Trek phaser and installed a blue diode laser in it. Here's his video of how he made it.
Update:
In the comments, Paul D says: "There was a long Slashdot discussion on this a while back, with a lot of informative links. Basically, the laser in a Blu-ray player or DVD player is strong enough to permanently fry your retina in less time than it takes for the blink response to kick in. These are seriously dangerous, people."