This is one that is hard to top...
I used to have a 1970 Porsche 914, that while probably the most fun car I've ever driven (And I've driven A LOT), it was in the shop at least once a month. Anyway, I used to take it to this specialty Porsche mechanic who usually had a VW Bug lying around for a loaner.
Well, when the loaner Bug was taken, what was left was a 1968 VW squareback. Not only was it an old, crappy squareback, but it would devour about a quart of oil every 50 miles. It had to be kept above the half-way mark on the gas gauge because it didn't work. It had a top speed of around 60mph and shook like you wouldn't believe at that speed. Also, when you tried to shift, you had to just move the shifter in clockwise circles until you felt it catch a gear...
Now the best part... It was big bird yellow... mostly... The rest was rust. On both doors was a white RIVITED ON sign advertising the mechanics shop. And to top it off was a bumper sticker that was anti-semetic, which my Jewish parents just loved...
