
Without a doubt, one of the craziest flattops Martin ever made, and it didn't really catch on either.
Of course, everybody will recognize the D-18E as the axe Kurt Cobain used on Nirvana's unplugged performance.

And another famous user was Tracy Chapman, who used one during her early days.
But neither used the guitar as it was intended. Tracy Chapman used hers plugged into the PA, like one would do with an Ovation. And Cobain had a Bartolini Soundhole pickup fitted because he hated the sound of the stock DeArmond pickups. The fact that he strung his up with Acoustic strings rather than electric strings also explains a lot when it comes to the resulting sound.
Because, if you use them as an electric, as they were intended to be used, they sound quite awesome.