one trophy per car, as an encouragement to try them all (or at least 100 iconic ones). Midget wheelie, flip over the tank car, the said "batman achievement" (citroen gt at night), photograph a sl55 using the sepia filter, win a practice mode race in chamonix using a 99 impreza, etc.
The achievement has to be described in all cars profile and in the usual trophy menu (ps3), not hidden.
Each one gives you a museum card of that particular car or related (brand, race, etc), and a ps3 bronze trophy. Earning 25/50/100/150/200/250/etc. gives you a silver trophy and a horn/paint/whatever (gold for every 200 or so, plat for all of them).
And as a 4th prize you get an awful lot of XP and credits for each bronze one (by car).
/Thread.