Here where I live now, there was a nice little Mom and Pop Mexican restaurant that served great food with super friendly service. Sadly, they closed a few months back and the building is now vacant.
When I lived in Alabama, "Sparky's" was the classic Mom and Pop. The building was ancient and about to fall down, but they made the best food and the prices were very good.
Lee and Ricks in Orlando Florida is another classic. Oyster bar with a poured cement bar and the best oysters I've ever eaten, but the building looks like it's sinking into the ground and the roof is rather "wavy."
Finally, "Golden Corral" in Brooksville Florida has wonderful food and all you can eat. It's good ole fashioned southern cooking which this ole Florida boy truly loves.