Not sure what your budget is, but I have a 2012 Infiniti G37 Convertible that's been great over the couple of years I've had it.
Pros:
- Fairly quick in a straight line (0-60 in the 5s, 325HP, 275ish ft-lbs of torque)
- Good in the corners, as the car is built on a 370z platform.
- Good luxury features, though the tech is outdated now. Leather was standard with cooled seats, nav, Bluetooth, rain sensing wipers, radar cruise control, etc available as options.
- Folding hard top means no one can slash your roof to steal things and it's quieter with the top up.
- Back "seat" makes a good parcel shelf.
- Japanese reliability for everything but the roof (see cons)
Cons:
- Back "seat" will not really fit adult humans.
- Folding metal roof was subcontracted to a German company. It's not nearly as reliable as the rest of the car. In two years of ownership, I've had two roof issues, though none at all with the rest of the vehicle.
- Gas mileage is poor.
- Trunk is almost nonexistent with the top down.
- Pre-2012 cars have a potential engine issue. It's about $2k to do a preventative maintenance which permanently alleviates it, or you can buy a 2012+ car that's already good from the factory.
- They stopped making them in 2015 (name changed to Q60 for that year), so they'll all be out of warranty now.
Price ranges from $15-25k, depending on age and mileage. I'd recommend one to a friend - apart from the roof, all issues are pretty minor and it's a fundamentally good car.