[Serious]

It's the e30 m3. The m1 and earliest m5/m535 put the m brand on the map but the e30 showed the world that BMW could do. The car completely redefines what you think is important in a sports car; it changes the perception that magazine stats like HP, 0-60, and skidpad numbers are what define a sports car and quickly things like steering feel, mechanical interface, and how a chassis communicates become the more important measuring factors of a sports car. It's that good.