A sleeper car is one that has an unassuming, often humble, exterior that hides serious performance chops – a car you wouldn’t glance at more than once, until it’s left you in its wake at a traffic light. Some of my current favorite sleeper cars include Volvo’s plug-in hybrid S90 sedan and the 375-horsepower Genesis G70 3.3T – but there are awesome older models that fit the bill too: the ’90s era Audi S8, and the Cadillac CTS-V Sport Wagon spring to mind. I’d also vote for the Audi RS6 Avant to be on the list, but there’s nothing deceptively mild about that car’s appearance. What are your favorite sleeper cars, or which one is the best of them all, and why?