On a similar note, I frequently use open C tuning...borrowed and tweaked from Jimmy Page: CGCGCE. That high E string can stay E for Cmaj, Eb for Cminor, and dropped down to D for like a whatever...C9 or something, I dunno officially or care. It's just a versatile deep sounding tuning that helps to break out of the box. Also works well on Acoustic or electric, from bluesy one finger barre chord progressions, eerie open string picking, or brutal metal runs. Slap a capo on the 2nd, 3rd, 4th, etc. frets and you get an open tunings in D, E, and above. It's havoc on yer strings to tune back and forth from open to standard freqently though. There's all kinds of other tunings, but I stay away from tunings with any of the strings going up more than a 1/2 step, cuz that's harder on the neck especially, as well as the strings.