The 50 Best Inventions of 2009

You fire a bullet, and it explodes where you tell it to. That's the essence of the XM25, a gun that fires explosive rounds able to neutralize enemies camped out behind cover. Using the gun's laser range finder and the bullets — which are equipped with microchips capable of registering distance according to the number of times they've rotated — a soldier can program a round to detonate beyond an obstruction — no impact required. The practical value? Soldiers in urban environments can fire over or past walls sheltering their enemies, and the bullets will explode on the other side. The weapon is currently under development for the U.S. military by Alliant Tech systems, Heckler & Koch and L-3 Brashear.