I am interested in hearing from folks who play rhythm guitar in standard tuning in Celtic music settings, particularly those who may have discovered unusual chord forms and voicings that are appropriate to Celtic music.
For instance, I often use a "neutered G" chord similar to a G minor but with the G string left open and the bass G note fretted by the thumb. In other words, it's nothing but G's and D's - no third - so it's neither major or minor. This lends a very bouzouki-like sound.
Anybody got any others?