I’ve always thought of the smell of gas as you fill up at the station to be oddly pleasant.
Try burning flour tortillas on the stovetop. Absolutely wonderful!
Yeah! Bean Oil! I’ve been known to fire up my chainsaw in my shop just to fill it with smelly goodness.
Of course, I ride RZ350’s, so I get my share.
Also, P-Tex and ski wax. I tune my skis and the shop is just full of smoke.
The smell of an old grocery store. With wooden floors.
Sends me back in time. Every time.
Plus the smell of fresh water and damp earth wherever vegetation grows, e.g., along a creek. Reminds me of playing Army when I was a kid.
Oh, yeah: The smell of green caps fired from a well-oiled Mattel tommy gun. And the smell of canvas (pre-synthetic) Army surplus gear and waterproofed leather.
Blacktop.
Whenever I drive past a parking lot being paved, or re-doing a road in the summer? Love it.
Y’all have named quite a few of my favorites already. Good ones, too.
One that may have gone by the wayside by now, and one I didn’t see already, would be the sweeping compound they used to sweep the floors in the elementary school where I spent my early years (back in the 40s). I always looked for that aroma in incense and room sprays! 
I could name a dozen of those, too, but they’re too traditional for the thread, I guess.
I’ve always been partial to wood smoke, especially from evergreens like pine and cedar. And I have happy memories associated with suntan lotion.
More standard: Anything containing real vanilla extract and/or cocoa powder.
Baked custard with nutmeg. Scottish shortbread in the oven.
Also reminds me of playing Army down by the railroad tracks, when kids could get away with that sort of thing.
I spent the summer of 2005 living in Jurmala, Latvia. Ten-minute walk through a pine forest to the shore of the Baltic. After more than ten years of living in a very polluted city (Moscow), this was pure heaven!
Cow manure on farms in South Central PA.
The smell of an old car. A pre-1975 car. In my family’s garage when I was a kid, late at night, when my dad was rigging something up to keep it going for a little while longer. It’s some combination of gasoline and oil and rust and vinyl. Whenever I get into my Corvair, the smell immediately transports me back to that garage.
I kind of like the smell of hospitals. I think it’s mostly the soap they seem to be partial to. When I was first dating my wife, and I’d meet up with her after she got off shift at the hospital, I’d tease her that she smelled like hospital soap. Now the smell always makes me think of that.
Puppy breath.
The smell of cats. Like when you put your nose into a cat’s fur.
The desert after a rain. The smell of light rain on dust and asphalt, as others have mentioned.
Play-Doh. Dang, I love the smell when you pop open a canister.
A new plastic egg full of Silly Putty when you first open it after finding it in your Christmas stocking as a kid.
When I broke the seal and popped open an old Aurora model kit, especially one of the monster model kits. That smell, that polystyrene smell. I’ll never forget it.
Newly opened Crayola wax crayons, cheap tequila, bicycle inner tubes, carbolic soap, and freshly sanded plywood.
A new board game, the printing leaves a wonderful smell.
Yep, unleaded gas does not smell as pleasant.
Old car smell. It’s generally the smell of antifreeze rotting the carpet mat. At least, I’ve had modern cars develop old car smell after their heater cores failed.
Old diesel fuel
Mineral spirits
Creosote
It’s been a long time, but I loved the smell of the ink on freshly printed mimeographs.
I am intrigued by the numerous times creosote is mentioned. The bush is very old.