5. Audi S4 (B5)
The late-1990s Audi S4 (B5) quietly set the standard for sporty sedans. With its understated styling and premium interior, few suspected the biturbo V6 and all-wheel-drive system lurking underneath. This combination delivered both luxury and stealthy performance, making it a favorite among enthusiasts who wanted to fly under the radar. Road & Track highlights how the B5 S4 became a true sleeper legend.