Some many to choose from. I think the leading contender would have to be Keith Whitley’s “When You Say Nothing At All”. During my five year stint as a country music DJ, this was the one song that I always stopped whatever I was doing and sang along with.
Other contenders:
“East Bound and Down” - Jerry Reed
“Driving My Life Away” - Eddie Rabbit
“Smokey Mountain Rain” - Ronnie Milsap
“Walk On” - Reba McIntyre
“Please Mister Please” - Olivia Newton John
“Ode to Billie Joe” - Bobbie Gentry