Straight to the top of this manufacturer's tree -- well, model line -- shoots the breathtaking 2017 Polaris Slinshot SLR. A bold, brave road beast, like the rest of its kin, it sports a 173-hp, 2.4-liter, four cylinder engine with five-speed transmission, but with added grunt -- and less weight -- thanks to the likes of forged aluminum wheels, a wider rear tire and open air intake.