While the GT2 is the champion of the turbo 911s, the GT3 dominates those with naturally aspirated engines.  Both supercars are really closed circuit animals but still legal on regular roads.  Porsche commercializes the GT3 since the 1999 model year and it has since been considered by many as the sportiest of all 911s, notably thanks to its turbo engine, its agility and minimal weight.  The GT3 is in fact the most widely raced Porsche car.