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.
A combination of up north (Carla knows what I mean, and Chance, too), gasoline, two-cycle exhaust, extremely cold air, wood smoke, books and something good cooking.
And that smell that bo spoke of
My grandma's soup cooking or her wonderful garden.
Musty mouldy smelling old mens clothes... if i smell that smell even now it makes me shudder
Cigars and onions
Hot Pockets and Hi-C Ecto Cooler (which did have a smell).
cow shit, chicken shit and horse shit. I grew up with farms all around me. LOL.