Not sure if this is cars seen on the street only but I'm always bragging about being at the ALMS race in Connecticut where the Audi R8 race car ran its very last race (shortly after the Audi R10 debuted in LM) and won the whole thing!! What an amazing car, here's the info.

http://asp1.walkontheweb.com/limerock/news_more.asp?id=11633