Early S197 Mustang GTs. The ones with the big headlight reflectors and bulbous fenders. Amazing how much a mild facelift can do to modernize the look of a car.
This. The whole design looked just plain and cheap, and the mirrors looked like they came off an F-150 truck. Besides, pretty much all of those "retro" designs, that were probably conceived as cars that would look good for years to come (or at least I imagine so in my head), don't age so well. Just compare the New Beetle with the Golf IV. It could be just me, but at least the Golf looks less ridiculous.
Another car that comes to my mind is the Mercedes-Benz W210. Not just that the headlight lenses make it look outdated, especially compared to the BMW E39, but they all look like they've done at least ten times the Earth's circumference under their wheels. I recently saw what appeared to be a well-preserved E 300 D, and it still looked like it was used as a taxi in Germany before being imported here. Not shape-wise per se, but what its design evokes to me.
The problem with Porsche is they're taking a 911 profile and streching on things that really shouldn't have the corporate look. Imagine a Mustang SUV, Mustang wagon or do the same with a Camaro or Miata. Now that they're making this vehicles into their own a little bit, the models look much more normal. Porsche 911 style is not like BMW or Mercedes where you can scale the corporate look into any car without it looking terrible. Even Audi to some extent has pulled this off.
And this is true as well. Design-wise, Porsche did great back when they had a classic-shape 911 and another classic shape for their transaxle cars. When the 996 and Boxster came out, things were still fine. But then they decided to make a VW Touareg look like a 996 911, and some years after that, they tried to transfer 997 911's body design language onto the Panamera. Not a good idea in my opinion. But they somehow managed to balance it out with their latest cars, now that the 991 and 992 911's don't have so much of the classic 911 shape, and that they've figured out how to transfer that body language on their SUV's and the Panamera, they look OK.
EDIT: One more comes to mind: the first-generation Opel Insignia. I still remember when it was new how my friend and I though Opel make lacklustre cars, and how the Insignia was a car that had some flair, some refinement in its design that sets it apart not only from other Opels but other cars in its class as well, however, ten years since it came out... I can't say the same thing about it.