Instantly recognizable classical pieces
Maybe most people won't know what they are, but some of them have, for whatever reason, become familiar to practically everyone. Name pieces that everyone knows.
I'm going to start out with a modern classical piece. Most familiar from some TV commercial featuring it:
Aaron Copland, the Hoedown from Rodeo (for reasons not clear to me, it's always pronounced "row-DAY-oh", so don't pronounce it "ROW-dee-oh" around cultured people because they will laugh at you.)
Peter and the Wolf, by Prokofiev -- this theme is totally familiar, I would think to practically everyone.
Danse Macabre by Saint-Saëns. We all know this tune.
What other classical pieces have entered popular culture to the point that everyone knows them?