Open D and G tunings (Vestapol and Spanish) are very common for bottle neck guitar.
Just dropping the G string down to F# is the lute tuning.
Then there is dropped D which as far as I know is the bass string.
Tuning the low E to D and the A to G is dropped G.
The lute tuning and dropped D are the only two tunings other than standard that I spend any kind of considerable time working with now.