Not a car per se, but for me it's a 2011 Ram 2500 Heavy Duty that disappointed. Wasn't mine - it belongs to my employer and I used it during a move. While it was useful for my purposes, holy CRAP I hated that truck. I'm not a truck guy by any means, so I'm already biased, but...
I totally understand why people joke about Dodge/Ram trucks being "shipping crates." The 6.7l Cummins turbo diesel? Nice engine. Oh, she's a thirsty beast - you probably get 0mpg city and 1mpg highway. But it has torque for days and runs pretty smooth. Everything attached to the engine though, just horrid junk. The transmission seems to rethink whether or not it really wants to shift into the next gear in the middle of doing so. The steering is so incredibly vague that any input you give is really just a suggestion. Once the bureaucracy inside the steering rack approves the proper paperwork in triplicate the truck may deign to corner. The brakes do NOTHING until you depress the pedal 1/3 of the way and then they lock up. It's like the brake pedal is a binary switch - it's either on or off, no in-between. The interior is the most uninspired, cheap bull crap I've dealt with in recent memory. I mean, it's a work truck, so I'll give a pass on that, but I have to mention it. It made getting back into my FiST feel like luxury.
As for a car that delivered? Well, I recently drove a 2015 John Cooper Works Mini Cooper S. Very fun little car. The extremely flashy design wasn't really my thing, but the car had it where it counts. Very nice performance, three different performance profiles from the factory, a pretty nice infotainment screen, and my favorite feature on the car - go-kart steering! You only need one full turn (or maybe less?) of the wheel in either direction to lock the wheels in that direction. That single thing made the car a real blast to drive and made it feel so responsive and nimble, right on the edge of being twitchy in fact. My only real complaint about it was how incredibly stiff the clutch pedal and shifter were. Made switching gears a bit of a workout.