Jeep Wrangler.  Says you are rough, tough and outdoorsy.  You don't shave very often, but you smell like pine trees.

Mustang convertible.  All-American sporty kind of guy.  But no laying rubber in front of the women. It doesn't impress them.  Really.  
Note to girls:  This is a good car for getting the guys' attention, too.  

A Mercedes always smells of money.  This is the CLK coupe.  It doesn't say, "I'm married with kids" like the bigger sedans.  It says something like, "I'm a young, unattached lawyer with lots of potential to move up (to bigger, more expensive cars)."

The Corvette.  The best car for picking up those 30-something divorcees.  But please, no cheap aftershave and jewelry because you'll send them away screaming (except for the really desperate ones).

Any Porsche will work.  This is the Boxster.  It means you're not quite as filthy rich as a 911 owner, but you are possibly younger.

Audi TT Roadster says you're stylin' first. To hell with function.

The Acura Integra if you're a college-age guy and looking for a young lady with tattoos and / or body-piercings.

Jags say "prestige" and "I have money to burn on unreliable, impractical trinkets."  This is the Jaguar XKR

Warning!  Do not try to pick up women with any of these vehicles!