Arguably one of the best-looking cars on the road, BMW’s 6 Series is available as a coupe or convertible. Using the same 500-horsepower V-10 as the M5, the M6 is the pinnacle of BMW’s style, luxury and performance. Although it still uses a fabric top when most droptops are using retractable hardtops, the 6 Series convertible offers the highest level of design, rigidity and noise reduction that is expected from a BMW. During the first four years of ownership, BMW 6 Series drivers receive a 50,000-mile warranty and $0 maintenance program in addition to an unlimited mileage roadside assistance. The BMW 6 Series gets an estimated 21-23 mpg on the highway; the M6 model tops out at 17 mpg.