Ralf Ottow was standing in front of his bathroom mirror one morning when he noticed that his forehead was sunburned. He hadnt been out tanning—his homemade flashlight had fried his skin.

If you need to temporarily blind someone, consider the DEF3. It's the latest flashlight dreamed up by the U.S. government's Defense Advanced Research Projects Agency (DARPA)-and designed by optics experts Science Applications International Corporation with flashlight maker SureFire-for use as an Army-issue non-lethal weapon.