I am a Senior Moment - so what?!

A lot of Jazz players use drop D for almost everything, a trend started by Howard Roberts a long time ago when he had a hit with "Moonlight in Vermont".

I find DADF#AC useful for some blues numbers, originally in open G tuning, that I cannot sing in G.

I use CGDGAD for a couple of things - I got it from Gordon. And I use CGDGBbD as well - I got that from Dave Evans, which is also where Gordon got CGDGAD (your secret is out, kiddo). You can get a really good range for accompaniment with those tunings, and some nice chords which don't sound like standard issue.

I once found a Nick Drake appreciation website with tabs and long discussions on the tunings he used. Frankly, a lot of the tunings were incorrect, so the tabs were w!@**, but it was interesting to try and play the tunes in the wierd tunings those guys had come up with!