Laser pointers, cat toys, et all.
The cheap laser diode devices.
    Yesterdays high tech is todays toy. These things have become so common, and cheap, that they no longer really even bear mention, and certainly are hardly worth the trouble of writing about. The current generation of laser pointers, pens, cat toys, etc. put out 1 mw or so. They are gaurantedd to be on sale at any flea market, gun show computer show, or fair. They are commonly available for under $10, though really high class models can be had for $25 or so, and professional pen pointers can cost near $100, and are available with multi color/multi beam options.
    All of these devices use laser diodes, an invention of the eighties. These diodes were intitially meant for use in home devices, particularly CD players. Most put out a red beam and are vacity lasers, with microscopic cavities.