Even though we think the guitar is near-perfect the way it is, inventor Sophie Léger is trying to improve upon it with the Tritare, a guitar with triple-ended strings. The Y-shaped instrument has one normally-fretted neck, and two others that don't have any frets and resonate the sound. You can see the two fretless necks in this picture — they're the ones upon which the guitar is standing.
The result is a highly unusual sound that's downright ethereal. It's more resonant than a conventional guitar, and the notes can be bent upwards or downwards for a slide-guitar effect. Best of all, the instrument is no more difficult to play than a regular guitar, and it can plucked and strummed, or even be bowed, or hit with sticks like a drum.
The instrument was first built in 2003, and there's a marketing effort going on at the website of the Tritare here.
Take a listen to this short composition played on the Tritare. It's like music from another world.