I'm not sure exactly how obscure this is, but it bugged me for ten years of my life, so I thought I'd share it with anyone in a similar situation.

"Intermezzo Sinfonico" from Cavalliera Rusticana by Mascagni

Tissue paper hawkers Kleenex used this in an advert circa 1982, which I have for posterity since my parents taped me lots of Christmas TV before I was born. The plot of this commercial is concerned with a small boy and his mother and father, who appear to be attending some sort of Communist rally in an undetermined location.
Anyway, the kid is separated from his parents by a marching band of Cuban revolutionaries playing the sort of exciting Latin/martial hybrid music usually associated with these sort of events (really, I shit you not). In floods of tears, he wanders into a local newsagent, where he is reunited with his dad, who gently lifts him onto his shoulders while attending to his tears with Kleenex. At that point, possibly the most gorgeous five notes strings have ever played swell up in the background as they leave the store.

I think if this advert was played to me in music lessons when i started school I would have a wider interest in classical music rather than the two or three rather arbitrary composers I have time for now.