Guitar is probably the most playable guitar app on iPhone, but it lacks one feature that apps like PocketGuitar has - support for open tuning.  Lots of folks play in open tuning, and we're not sure how to name those non-standard chords.  How about an option for us to define the tune of each string, and save non-standard chords (e.g. into chord 1, 2 etc) for playing later?  That would be awesome!