it depends what you like. I will list some of my favorites!
Rumspringa - This is a documentary about the Amish people. When they turn 18 they experience Rumspringa, a time when they can go out into "The Devil's Playground" (the real world) and do things like party, smoke, drink, do other drugs, USE ELECTRICITY! Then they decide if they want to stay Amish or not.
Eathrlings - A documentary about the way humans abuse animals in the industries of food, entertainment, fashion, science...etc. It will make you think and hopefully make some changes.
Raw For 30 Days (not out yet) - A documentary coming out sometime in Spring about 6 long term insulin dependent diabetics (One Type I, the rest type II) who went raw for 30 days. After only 4 days they were all off insulin and after 30 days they were all cured (provided they stick with the lifestyle).
Heima - A documentary about the band Sigur Ros' tour through their home country of Iceland. The music is amazing and the places they play at are awesome. Iceland has gorgeous scenery.
Gaza Strip - A documentary about what average life is like for the Palestinians living in the Gaza Strip.
Occupation 101 - A documentary showing the history of the Israeli-Palestinian conflict up to today and talks about what the Israeli's do and other factors like US support and stuff.
I was gonna list a bunch about religious stuff but I forgot most of the titles

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There was one I saw about Noah's Flood how they tried proving it and it was interesting (they found chariot wheels in the Dead Sea, they found a rock with a little erosion supposedly where Moses hit it with the stick, and they found some hills that were black at the top).
Jesus and the Shroud of Turin is another interesting one. It's about the Shroud of Turin they found and talking about if it is really authentic or not.
Oh and Jesus Camp! That one is pretty crazy if you haven't seen it yet!
Also Inconvenient Truth is gay Al Gore is a hypocrite.
Also also
Planet fucking Earth!