Wow, I suck at this! 30/50, but only because Jake gave away #25! (I thought it looked like a Pinto or Gremlin or something). The Cayman took me forever - I had Porsche, and I kept going through boxster, 993, 996, 997, turbo, 911 turbo, even though the brake ducts led me to only boxster and 996 turbo (right?). Stupid Cayman
#17 is definitely tricky, but try to picture that "rickety" look in a larger sense!
One interesting thing I noticed was even when I was wrong, other guesses would be from the same country - makes me think there must be a common thread to German cars, British cars, Italians, etc. (except #12 - I'm stumped - looks like a Beetle, or maybe a Bentley...)