In perfumery, the worst smells can have the best effects–the inky, moth ball fragrance of indole lends a natural, velvety note to floral compositions; aldehyde C-11 with its dirty hair facet makes rose accords rich and lush; animalic notes lend a surprising sensuality to woods and resins. Thinking about it made me wonder about preferences for scents that are considered by most to be bad or unpleasant: skunk, hot asphalt, gasoline, mildew, etc.
My own good-bad favorites include the musty smell of decaying leaves in the fall, the rotten onions and cheese of durian (a notorious tropical fruit,) and the pungent sweetness of pen ink. I also love the smell of jet fuel on the airport runway; although these days with the boarding taking place via covered passageways, one rarely gets to be on the field itself.
Photograph of fallen leaves via wikipedia commons.