This is a really difficult question and there are so many variables -
Is it my one and only car (Audi RSQ8)?
Can I sell it and use the proceeds (Stirling Moss' 300SLR worth >US$100MM)?
Do I presume that if money is no object for one single car, then I have all the money I want for other cars as well and I'm basically just naming the most expensive car I'd buy (McLaren F1)?
Can I has 5 cars instead?
Wife's kid hauler - Lincoln Navigator (until the new Escalade lands)
Vaguely practical car for "dad duties" - Audi RSQ8
Bad ass "daily" driver - Ferrari 812 GTS
Nostalgic bedroom poster car - 2001 Lamborghini Diablo 6.0 w/ GT body
Crown Jewel - McLaren F1
Edit - damnit, I'd want a vintage car too (Ferrari 250SWB)... And maybe an F50 instead of the Diablo. But then, where can I slot in a Carrera GT? And then for a vintage car, maybe I want something even more striking, like a DB4GT Zagato. But if my main concern with the vintage car isn't performance, but rather, aching beauty, what about an Alfa Romeo T33 Stradale?