I'll third the Miata plus I'll throw in the BMW Z3. especially the M Roadster version (S52 engine) as I have been behind the wheel of all three (including the S2000), the M Roadster is the punchiest, the Miata is the lightest and the S2000 for me is not fun around town or DD use as its a complete DOG under 6K RPM compared to the others, the others might not have as much top end, but are way more peppy and responsive. The Miata and S2000 are similar handling wise. the M Roadster has a interesting feeling that I like with the long nose and you're sitting right over the rear tires, its like you're on rails around corners.
The BMW Z3 is close to becoming a classic car with production only from 1995 to 2002 (Wikipedia). I've never driven a Z3, though my buddy Nick and I know a guy in our sports car club with a Z3 M Roadster. They're even smaller than the S2000 or the Miata with only enough room in the cabin for two passengers and almost nothing else. The Z3 also doesn't have the legendary Honda or Mazda reliability. The Miata is really light, has a well matched transmission and has invigorating pick up. The S2000 has a stronger engine than the Miata, but it's also a heavier car that has to be revved harder for a thrill ride. With that said, I can see why the Miata is one of the greatest roadsters ever made with nimble handling, ample power, and an affordable price. If an older model Miata or S2000 shows up for sale, I'd give either car serious consideration
