Those who are torn between a road and mountain bike are well-served by the Bad Boy from Cannondale, which is the only company to offer a bike of this particular type. It includes an aluminum frame that’s virtually identical to mountain bikes the company makes--meaning it’s rugged and has the stable handling required for riding off-road. But the Bad Boy comes equipped with 26x1 tires, which are narrow as those on a road-racing bike. This makes the bike accelerate quickly and offers low rolling resistance for longer rides on the pavement. Other equipment, such as the wide-range 27-speed gearing powerful Shimano V-brakes and flat handlebars, are standard-issue mountain bike. This unlikely combination of components yields a bike with tremendous versatility: As equipped, it’s great for riding city streets, bike paths, etc. But a spare set of tires--figure about $40 for a pair of knobbies--lets you take the bike on to rugged trails. One drawback for off-roading, however, is that the Bad Boy has no suspension. Bonus: The understated flat-black color scheme shouldn’t catch the eyes of thieves if you lock the bike outside.