For me, it's a sunroof. My Grand Am had one and I had it open more often than not. The sun and extra light in the interior made it a favorite feature of mine. I'd love to have a convertible, but they are just too impractical for me. A sunroof is a happy medium, I guess.
I've seen a Mazda3 identical to mine save for color and it had an aftermarket sunroof...and it looked awful. Won't be considering that option, ever. Back in the '90s, my mom had a Corsica LT and had an aftermarket sunroof installed. It leaked like a sieve every time it rained and eventually, my stepdad siliconed it shut.
Have a classic Mazda RX2 for your time.