I'm not a huge fan of American cars (besides the 4Runner, we also have a Tacoma), but I'm surprised no one mentioned the Mustang GT. You could get a nicely loaded convertible GT in that price range, especially if you wait until February to buy one. Also the GTO might work, even if the price tag might be a little higher than $27K.
To those that mentioned the G6 coupe, that seems like a pretty reasonable choice and is least likely to have astronomical insurance costs for a college student under 25. I had a 2000 Grand Am GT Coupe. It was fun to drive, and it had a decent amount of power, but it was a maintenance nightmare. Thank God for warranties. That said, hopefully the G6 won't be plagued with these issues. A 240 hp V-6 in a car that is presumably lighter than its predecessor sounds like a pretty good match!
I still prefer Japanese though. I like the new 350Z's. I took one out on a test drive and had it to 90 mph in no time at all. It handled really well also. I also drive a new RX8, and that car likes to be driven hard and fast. Also, it does have a fairly useable back seat.
I sure wish Toyota hadn't dropped out of the sports car market. The last Supras were bad ass. I even liked the last MR2's. It's depressing to know that the sportiest offering Toyota has is a SCION XC!!