Back when I was younger, the Lamborghini Murcielago was what I'd always wanted. And I'd still be totally cool with it. Sexy as hell, although it's been succeeded by newer models. The Reventon's (look at Kura's post) a sexy beast, too.
A small remark to the Fiat 500, it's an odd car. The commercial for it from last years Super Bowl was hilarious.