Porsche 911 is the most iconic sports car the world has ever known. A big part of its distinction and appeal is its rear-engine design, but few consider that the ideal layout for a performance car. Many exotic cars and purpose-built race cars -- and Porsche's own Boxster and Cayman -- feature an engine placed behind the driver but ahead of the rear wheels. With more of the weight situated near the center of the vehicle, mid-engine vehicles are able to change direction more quickly and easily. The 911 will be Porsche's flagship for many years to come, but the Cayman S may be its purest sports car.