I've put on "black face" twice in my life. Both times were for Halloween. In second grade I wanted to be the next Bo Jackson, so I dressed as him for Halloween. The second was in 2002 when I put together a pretty sweet Humpty Hump aka Shock-G costume.
I was really proud of the second one. I probably wouldn't do that these day. I wonder if anyone was offended. I hope not.
Edited to add: I didn't even know what black face was back then tho.