Ive been using open c for about a year now due to its simplicity. The concept of playing the same shape up and down for the lowest 5 strings makes it too easy to improvise and write songs.
D modal tuning (D A D G A D) works the same way but the G string is skipped instead of the high E like open C.
This tuning was probably most famously used by Jimmy Page in Kashmir or Andy Mckee in Drifting.
If anyone thinks this is cool or useful, throw in your 2 cents.
Feel free to ask any questions.
Keep Playing.

It's cool, and useful. Though I wouldn't say I skip out the G. Have to be aware that I have to fret it differently to the other strings in each key, but it's the same with the E string for open C. Though possibly more in the way...