Freshly cut grass, petrichor, a pine forest, extremely cold air (stolen from Bozette's comment above), and diesel exhaust.
Mothballs. My Great Aunt used to visit every Sunday.
Garbage. My childhood was no bed of roses. While my parents might have been wonderful it was those around me that weren't.
And that smell that bo spoke of
My grandma's soup cooking or her wonderful garden.
Cigars and onions
cow shit, chicken shit and horse shit. I grew up with farms all around me. LOL.