Ooh this should be difficult as documentaries don't often spring to mind really quickly. Apart from the Mcdonalds one. Which was entertaining enough, even if it left a sickly taste from the subject matter itself.
My documentaries usually are BBC fare and only an hour long. Something tucked in an evening schedule. Documentary series, now that is easier, The World at War springs to mind immediately.
So I'm going to cheat a little and swap around one of my previous choices...not that anyone will notice so...
etre et avoir
A very simply done documentary set in a small, rural French school. It highlights a different side of France from the romantic expat wishlist that is shown constantly here. Quiet and thoughtful the teacher and his little class are nevertheless entertaining in their daily life and the highs and lows of school.