Austin Mini. A car that never made a penny of profit for the manufacturer. A car that had its seams on the outside. But they sold several million of them.
It was a pretty neat peace of engineering in many ways and great fun to drive if you didn't want to do too far. Continuing to build it for 40 years at a loss is more about a lack of management than a design fault in the original product.
The same company managed to sell about a million Marinas/Itals and that really was a terrible piece of engineering but no doubt it made them money, if only because the developments were negligible as it was probably designed on the back of an empty Woodbine packet after about 14 pints while the engineer was passing the time waiting for a taxi home.