A cool hoverboard would have a sleek and modern design, with LED lights for added visibility and style. It would have powerful motors for smooth and fast movement, and a sturdy build for durability. It would also have a Bluetooth speaker built-in for music listening while riding. Additionally, it would have advanced safety features such as a built-in GPS tracker and automatic shut-off in case of low battery or other safety hazards. Overall, it would be a cutting-edge and stylish mode of transportation that combines convenience, entertainment, and safety.