Sold my GTP, missed it a ton, eventually got another one that was VERY similar. Ended up selling that one too, lol.
Sold my Z28 because I had to, not because I wanted to, and definitely miss it. If I can't afford a nice C5 in the next year or so, I'll probably get another Camaro just like it (but a different color that I like better). I hate not having a quick car, it sucks.
I miss every car I've ever sold, but the only one I truly miss/regret was the Z28.