I always include the color of the car in the name.
My 986 is Arena Red, so her name is "Scarlett". My silver Honda is "The Silver Beep" (a milder variation of "The Chrome Horn"), and my white 240SX was "The Great White Hope".
So I'd pick something with "Gray" in the name, like "The Gray Ghost".
Pdwight's suggestion is particularly creative, I think.
Just sayin'...........
TO