3. Buick GNX
The Buick GNX stands as a legend among sleeper cars. Outwardly, it resembled a mildly menacing version of the Regal, but its turbocharged V6 engine transformed it into a genuine powerhouse. In the late 1980s, it could outrun most V8 muscle cars, shocking rivals at every stoplight.
With its stealthy, blacked-out design and discreet badging, the GNX became a cult icon and a feared street racer. Hagerty calls it the quintessential American sleeper.