Oh man... There's no way I can pick just one car. Absolutely no way. But here are some that come to mind:
For special occasions: Aston Martin DB11 or Vanquish
For track days: Porsche 911 GT3 RS
For an elegant night out: Aston Martin DB5
For historic racing: Jaguar E-Type Low Drag Coupe
For going naffing fast on the autobahn: Mercedes SLR McLaren
For going naffing fast through a Swedish forest: Mitsubishi Evo IX
For going naffing fast period: McLaren F1
For delivering pizzas really fast: Ford Sierra Cosworth
For my architect costume on 90's night: Saab 900 Turbo
For going quickly but in a kind of French way: Renault Clio Cup
For going French: Citroen 2CV or DS
For wearing aviator goggles, growing an excellent mustache, and making people smile: Morgan 3-Wheeler