Series1- My wife had a 3rd generation RX-7 and I absolutely couldn't fit in it; couldn't get enough room between the seat and wheel for my legs so I couldn't heel & toe when shifting, which made it pretty much undriveable. I'm a lean guy, so if *I* couldn't fit...
Oh, and it was very fragile too, it'd dent if you gave it a hard look. Check one out, but make sure it's right for you.
While different from the Viper, its clutch/stick wasn't the easiest to work either (FWIW I learned to drive a stick on a 1st gen. RX-7).
People who buy the Jeep STR-8 seem to find it less fun than they expected, not sure why but you see a lot of them for sale with hardly any miles on them
What about a BMW? I've had a few M3s of various vintages and they're great. We drove them at a driving school and I've loved them ever since. EASY cars to learn with and fast/serious enough that you won't get bored.