As a counterbalance to the cute utilitarian bikes above, the Specialized Turbo Levo FSR Comp is a big, bad, and burly mountain bike. With 27.5-inch wheels, massive 2.8-inch tires, 150mm of travel in the front and 135mm of travel in the rear this bike is made to shred. The Specialized 1.3 Rx Trail-Tuned motor is designed specifically for off-road riding and features a double freehweel design that disengages the gear box at top speed to reduce friction while ripping downhill. The low center of gravity and stout parts make this one a relatively nimble handler that is ready for the rowdiest downhills.
E-bikes mostly use motors and battery options from a few major suppliers: Bosch, Yamaha, Shimano, and Brose. A few other brands exist, but are less reliable or powerful. Some, like the Yamaha system, have more torque and others are quieter. But generally all four make good options. Look for motor output (in watts) which will give you an idea of total power. But watt hours (Wh) is perhaps a better figure to use—it takes into account battery output and life to give a truer reflection of power.