thinking about it more, i think a car needs some special significance to you personally for you to never get tired of it, and have it be something you keep forever.
like for me, the 911 has unwaveringly been my favorite car of all time. and this is the most ultimate version of the model that i can afford. a Ferrari probably floats most people's boats more, though. i brought this question up at dinner tonight and the answers i got were -
'63 Corvette convertible