25. 2nd-Generation Prius
Yeah, it's boring as all hell to drive, and producing them creates so much extra carbon emissions that it isn't actually any better for the environment than a regular car, but no car has done more to push alternative fuel technology forward. This was the first alt-fuel car to sell en masse and the world has never been the same since. The 2nd Gen Prius is easily one of the biggest milestones in automotive history.