Well, that's a rather broad question, a wide-open question.
I'm going to turn the question around, though--what sort of documentaries do you like?
And then one can go from there.
I recently watched.....and re-watched.....and re-re-watched.....and re-re-re-watched the 1970 movie, Waterloo, which wasn't a documentary, but I suppose close to being one (I had to watch it several times because I'm deaf and miss things. If I watch something often enough, sooner or later I finally grasp the whole thing).
A historical re-enactment, I suppose.
There's straight documentaries too. So.....tell us what you like to watch, or what you'd like to see, and we can go from there.