It depends on the style of music. Eddie Condon, the jazz impresario and tenor guitar player tuned his like a plectrum banjo, C,G,B,D

I would think that otherwise the DGBE. Anyone know what tuning the tenor guitar player for the Delmore Brothers used?

You might also try what's known as a re-entrant tuning. An example would be a ukulele
gCEA or (like Ukulele Ike) GCEA with the first string an octave lower.

I think tuning it like a mandola CGDA might work. I personally like the CGBD plectrum tuning better.