"Row, row, row your boat" is a two-chorder that you can fudge into a one chord song. If I meet someone who wants to learn to play guitar, I teach 'em one chord and have them strum this song. Everyone knows the song. It is a round, so it can go on for a long time with its minimal words. Finally, because it is really a two chorder, the student begins to get a sense of how a melody "calls" for a chord change.

Roger in Baltimore