In my high school speech class, my "demonstration speech" was on the history of metal (up to that point, of course). I went up to the front of the classroom with a boombox and a stack of cassette tapes and educated my classmates on Black Sabbath, Judas Priest, Iron Maiden, Metallica, etc etc. I got an A.
In my college speech class, my "demonstration speech" was on how to play the guitar. I showed ppl how to play a few simple chords and scales & stuff. Also played the better part of Iron Man. On an acoustic. I got an A.