i guess that really depends on what you want it to do...
if i could only own one car for the rest of my life, I think it would have to be the BMW M3. Fast, classy, reliable, decent on gas, and a joy to own/drive.
of course this negates any practicality of transporting more than 2 people, towing, winter driving conditions...
My favorite car is the Porsche Carrera GT. It's super fast, super hot, super sporty... it's a super car! I'm not much of a truck guy, but I really like the GMC Sierra Denali. That's a nice truck!