Well, I'd never seen a photo of a Mayback Landaulet but now that I have, I think that thing takes the cake!
I also think the Nissan Cube is the ugliest of "normal" vehicles -- those cube vehicles (xB etc.) are all pretty ugly, and that offset rear window is hideous. Even worse, since Japan is right hand drive and US left hand drive, the ugly window's on the wrong side to actually improve visibility any useful amount!
Runners up? Lincoln Navigator (all recent Lincolns have ugly grills, and big boxy SUVs are ugly in general), Hummer (if they are still making it?, I think Hummer was sold off). I agree the Mini is pretty pointless (with that low of gas mileage for the size of vehicle) but it's a lot less ugly than these other vehicles IMHO.
Camaro? Really? I think it looks OK. I could see not liking it but you really think it's uglier than the other cars people have mentioned? They're pretty bad.