However much fun it is to barrel down a mountainside on two wheels, it's equally painful to pedal those heights in the first place. Unless you've got this 1200-watt motor kit handy. Then it's pure joyride.
The Ego-Kits E-Powered Downhill Bike Kit is a mountable motor that's compatible with 70% of bikes out there. It also includes a battery pack, crankset, chain, throttle, and charger to ensure it lasts your whole ride. Which, by the looks of this promo video, is going to be happening some pretty far-out places:
Sure, just riding to the top of a mountain might diminish your sense of accomplishment. But think of it this way: you just kicked gravity's butt without breaking a sweat. That sounds pretty accomplished to me.