hmm... a long time ago I was given the "pleasure" of driving a Ford Festiva. Wow, what a piece of crap. Older Kias, and any American compact car (Neon, Cavalier, Sunfire) are also at the top of my list.
The funny thing is... there was a very similiar thread on the Porsche forums and a lot of them named my Lotus as one of the ugliest cars on the road:
I think she's beautiful but I guess beauty is in the eye of the beholder