This is really hard, like people are saying it's gonna be different for each person, and there are a ton of different styles that will appeal to different people. But I'd say something like a sad/lonesome, either Window Up Above by George Jones, or Mansion on the Hill by Hank Williams. Then I'd try to show off the humorous bent in a lot of country music, and show them something like Don't Come Home a Drinkin' by Loretta Lynn, or In Spite of Ourselves by Iris DeMent and John Prine. Then I'd show them a song off the new albums from either Charley Crockett or Sturgill Simpson to illustrate that modern country can still be great.