I limit myself to just a few tunings outside of standard and one I really like is Malagasy- CGDGBE (low to high). I learned R. Thompson's '52 Vincent Black Lightning in it and subsequently arranged Ashokan Farewell, Planxty George Brabazon, Bonny Lass of Anglesey and a few others. It's also useful for playing blues in G as you have the I,IV,V in the bass on the 5th, 6th and 4th strings respectively and the familiarity of standard tuning on the top four strings. Open-C is close by as well.

Frankie