The Original Electric Car: Unplugged?
Perhaps the most notorious suppressed invention is the General Motors EV1, subject of the 2006 documentary, Who Killed the Electric Car? The EV1 was the world's first mass-produced electric car, with 800 of them up for lease from GM in the late '90s. GM ended the EV1 line in 1999, stating that consumers weren't happy with the limited driving range of the car's batteries, making it unprofitable to continue production.
Many skeptics, however, believe GM killed the EV1 under pressure from oil companies, who stand to lose the most if high-efficiency vehicles conquer the market. It didn't help that GM hunted down and destroyed every last EV1, ensuring the technology would die out.