2007 Mercedes-Benz CLK-Class CLK550 2dr Coupe (5.5L 8cyl 7A)
I previously owned a 2003 CLK500 and let me tell you that the new 550's engine completely blows away the previous version. The accelleration and overall performance is incredible. The exterior and interior are stunning. Practically every time I drive it someone is telling me how beautiful it is. Go get one today.
Pretty much everything, but if I had to pick one, the engine performance.