18. Mazda6 MPS/Mazdaspeed6
The Mazda6 MPS (also known as the Mazdaspeed6) took everyone by surprise in the mid-2000s.
Its conservative sedan styling masked a turbocharged 2.3-liter engine and all-wheel drive, generating 274 horsepower.
This hidden power allowed it to shock BMW and Audi drivers at stoplights and on twisty backroads alike.
The Mazdaspeed6’s blend of stealth and performance made it a sleeper that’s still celebrated by those who appreciate subtle speed.
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