Tern Verge X10
This bike is featherweight, lightning fast, and tough enough to take on rough terrain (and city potholes). Best of all, it folds up superfast, so you can easily carry it into your building or stow it in your trunk. The 20-inch Kinetix Pro X wheels, 10 speeds, and adjustable stem and seat mean you can even take the bike on long distances without sacrificing comfort. ($1,950, ternbicycles.com)