Triple 8 Wristsaver

Hands down the most critical piece of protective equipment (besides your helmet). 

The Triple 8 Wristsaver design works like a splint, with a bar of plastic on either side of the wrist. It effectively prevents you from bending your hand back and spraining or breaking your wrist. The Triple 8 Wristsaver also features a slider on the palm to prevent road rash when falling on hard surfaces.