Spotted in the MAKE Flickr pool, from Sascha Grant:

I purchased a 405nm laser diode…off ebay just recently and needed a case to mount it in. So I have turned this from a length of aluminium tube for the body and two pieces of aluminium bar for the front and back closures. The front closure doubles as a heat-sink. Everything’s held together with grub-screws. Runs off two AAA batteries which just fit inside.

More:

• Laser transmits audio using frequency modulation
• Arduino-based game controlled by laser pointer
• Building a real-time 2D laser range finder
• Laser tripwires for Machine Project art heist
• How-To: Drill press laser pointer