Surly Pugsley with BionX Motor

Surly's Pugsley is already one of the great fat bikes, a kind of mountain bike with oversized tires for extreme off-road riding. Surly slapped a BionX motor on the Pugsley to make a machine that can roll over just about anything — sand, snow, or mud. With the motor set on pedal assist, riding this bike through golf-ball-size gravel was no problem. And going uphill on asphalt — where the massive, nobby off-road tires don't usually excel — was a breeze with the motor running at full-tilt. 
[$3,800; surlybikes.comridebionx.com]