Probably the uncensored declassified Holocaust photos which were labeled as being "too graphic" for the press but were still put in the government files to document what was going on. (I work at a place which archives video and photos)
A close second would have to be an old video of a "black face parade" which consisted of about 30 people in black face, 20 people in yellow face, and about 10 people dressed as penguins who also had black face.
