The US Department of Homeland Security has funded the creation of a non-lethal weapon called the Dazzler that's basically a flashlight that causes disorientation, nausea, and vomiting. Now you can make one too! Hardware hackers from Adafruit explain it all.
If you aren't a fan already of the hardware hackers at Adafruit, this educational video will win you over. They've done a little research, and turned the DHS's million-dollar weapon into a $250 home electronics project called the Bedazzler.
This has got to be the greatest mad science project ever. If you build one of these, I fully expect you to shine it on your frenemies, take video, and post it here.
via Adafruit Industries (Thanks, Phil Torrone!)