58: Pontiac Aztek
On top of being one of the ugliest cars on the road, the Aztek was also unreliable. GM threw this car together with a lot of recycled parts causing the design to be faulty. The engine was known for intake manifold gasket failure, which would then cause the car to overheat. The oil and the coolant would mix and cause the engine to sludge (via Hot Cars).

This was a catastrophic failure by GM, one that cost the company billions of dollars to rectify. If you weren’t lucky enough to have an Aztek that was part of the recall, you will pay dearly for the repair. The transmission in these things is also questionable and tends to go out often when the car racks up the mileage.