Another vote for open tunings here. Their chief advantage for me is that it's easy to play "self-accompanied" melodies. The lower strings provide appropriate bass notes that are always there to be used with no left-hand work involved. That allows me to devote 95% of my meager mental capacities toward playing the melody on the higher strings. And some of those melodies can be incredibly simple and still sound good if the open bass notes are used to fill the sound out. I have some versions of songs where the melody part is played almost entirely on the first string. It would sound insipid if I tried to do it in standard tuning, but it works in open tunings.