Agreed, this is a debate that can go on forever. There are SO many "significant" cars, in terms of technology, styling, performance, etc., that theres no way to make a list that everyone would agree on.
Ok, so define what "car" means. That in itself can be debated, there is no one definitive answer. I mean, somebody could conceivably say that the Cugnot steam wagon of the 1700s could be called the first car... it all depends on how you define the term. In my opinion, the first "car" as I define the word was the Benz Motor Wagen.
VW Beetle, Model T, of course, obvious entries on the list. And tons more.