The Aerotrain really may take the cake for sheer beauty in industrial design, but it isn't a car.
I took a look at the Nissan "Joke" and decided that anything that tried that hard to be ugly deserved to be even uglier, so I had a little fun with Photoshop. The Juke may not be the ugliest car ever, but I'm not aware of an uglier one in current production.
Historically speaking, the French have given us at least their share of genuinely stunning automotive designs. The Citreon 2cv has been mentioned. I don't know that any one manufacturer has produced more absolute jewels than VOISIN .