My Dad wasn't really a car guy. It was just transportation to him....so, I would have to say his 3 on the tree '58 Ford Country Sedan Wagon. It had a hole in the rear floorboard and we kids would drop paper through it and watch it fly up into the air behind the car.
What a blast.

Funny story about it...Years after he sold it, we were at a local park and my Dad spotted the car. He was over looking at it when the new owner walked up. My Dad says, "That used to be my car. Yeah...sometimes I wish I still had it." The guy looks at my Dad and without missing a beat says in perfect deadpan fashion, "Yeah...Sometimes I wish you still had it too."