The first songs my sister got into were 8VM and SDOIT.
But she's been around me listening to it for years so she's used to it. If they're new, I'd show them PMU, Overture 1928/SDVu, As I Am, Endless Sacrifice, TRoAE, CM, OtBoA, TEI and BtV. Those all seem to cover all their styles without going too extreme if they're only just starting to get into them.