Quadrocopters are everywhere these days. But the 20-gram CrazyFlie is one worth noting.
The first thing you'll notice is that the circuit board is tiny! In fact, one of its sides is only 8 cm, and the whole thing easily fits in one hand. Yet there's a CPU on it that helps the quadrocopter make 250 adjustments per second by using info from its 3-axis accelerometer and two gyroscopes. And after watching the video you'll see how, despite its cheap look, this thing actually keeps pretty good balance. The operator (pilot?) controls the copter with a gamepad, and a nearby computer sends the input commands to the quadrocopter's radio receiver.