Great/Good clical pieces?

For me, anything by J S Bach. Otherwise, for nice accessible pieces readily enjoyed by a listener inexperienced in clical music, I'd suggest Orff's Carmina Burana, Grieg's Pier Gynt Suite, Ravel's orchestration of Mussorgsky's Pictures at an Exhibition, and Mendelssohn's Midsummer Night's Dream, among many others. But those are a start.