There are a few one chord songs out there....such as the song,"Low Rider." I decided to try and write one of my own. I love the old stories of the wild west so I thought I would write a story of a man who had been wrongly accused and murdered. His Ghost enters into a stranger to get revenge.
It turned out to be one of my favorite songs. I tried to make the music a little haunting and keep the riff rolling. You can do a lot with your vocals in a one chord song. The music tends to be more mesmerizing than songs with chord changes.
Try writing one sometime...I bet you'll like it.