Another vote for skunk here. Unlike most of the other folks who’ve posted, I have yet to have it be strong enough that I didn’t like it. I’ve never been sprayed, though, so that might change my mind if it were ever to happen.
New shower curtains
Play Doh
Pimple pus (either the real greasy stuff or smear the waxy plugs between your fingers to release their aroma)
Ear wax
Baby Magic bath
Creosote like you smell in the subway
Sawdust
Fireworks
Is it odd to be an emphatic nonsmoker and still enjoy the smell of tobacco?
I’m in a play right now where I carry a prop pipe, and during downtimes I’ll occasionally take it out and stick the bowl up to my nose and have myself a big satisfying whiff.
But if you asked me to actually smoke it, I’d probably barf.
Smoke it with tobacco, I mean.
[insert 3 foot tall, blinking, projectile vomit smiley, with sound effects]
Good Og!!!
I like the way the inside of my truck smells. It is 26 years old, all old cars have a smell.
I like the way carberator cleaner smells (much experience, see above.)
Hot Dr. Pepper with lemon in it, cures everything.
I like the way beer smells on an August evening.
Fax paper.
Office staples and paperclips. They have a similar smell like a big jar of coins…
Goats.
I love the smell of a new school box. Not the plastic ones kids get now–no, I’m talking about the old-fashioned paperboard kind that I used when I was a kid. I found one like that a couple years ago and couldn’t help myself–I opened it and took a big ol’ sniff! Yep, it still smelled good! 
I love the smell of an orange juice factory. Kind of a sweet, burned orange smell.
I always loved that smell too, but it’s hardly noticeable now with the newer kinds of spouts.
In a similar vein, I always loved the smell of jet fuel at airports. The smell, the sounds of airplanes landing and taking off still reminds me of when just going anyplace on a plane was a big thrill. At least I thought it was jet fuel, but I suspect it may consist just as much of the exhaust from cars circling around the arrival and departure terminals.
I love the smell of those “cum” trees. I think Cecil did a column on them many years ago.
I grew up in Ohio and had to cut the lawn frequently. I now live in the southwest where desert landscaping rules. One morning, while riding my bike to work, I went past a schoolyard where the grass had very recently been cut. I could not believe the flood of memories! I was instantly 30 years younger and back in Ohio. What a fantastic smell.
Trains coming into the station. There’s this hit of hot metal and dust and oil or something, I’m not sure exactly what, but I love it.
And dust, that dry, earthy smell. And fresh concrete when you’re walking past a building site. And fresh paint. There’s something about fresh paint that smells of possiblity.
And I love the smell of tomato leaves, it’s sort of the scent of tomatoes X 100. And glossy paper, like expensive wrapping paper or expensive catalogues.
My family laugh at me because I’m always sniffing things, but just about everything has a distinct odour, even people.
There is a perfume company called L’Artisan who make scents that try and capture unusual odours, including one that has a distinct top note of petrol.
http://www.artisanparfumeur.com
I know the perfect job for those of you who love gasoline smells. My old job in the oil patch. Not only do you get to smell those smells, you get paid to put your sniffer to use walking line! Woo!
I would, however, not recommend that you stick your head in a nearly empty tank on record hot day and almost pass out from the fumes and fall in. Just saying.
I like sharp smells. I hate perfumy smells.
And I love to bury my face in my cat Halley’s fur. She smells like powder. Irving smells like cookies and makes me hungry. The back of my husband’s neck occasionally smells like fireworks. He claims I have a brain tumor. 
Interesting topic.
Add me to the list of roofing tar/asphalt. Both for the smell and the notion that it represents society in motion.
I like the smells of electronics and cork. They remind me of stereo equipment (its the smell of sound).
Leather. Reminds me of my Dad when I was a kid.
What?
He used to work in a leather factory and I could always smell that he was home before I saw him.
A hint of horse/cow manure on the breeze. Nothing says ‘countryside’ better.
Fresh photocopies.
I think most people like that (except chronic hayfever sufferers, maybe!), but for me it has to be mixed with two-stroke exhaust (i.e. grass being cut with a petrol mower) to be perfect.
Mothballs. My ex-girlfriend always smelled of mothballs when the weather turned cold. It still reminds me of her.
I love the smell of Tiger Balm (an anesthetic topical cream). My friend gave me some for my mosquito bites. At first, i thought it smelled terrible, but i didn’t have any medication, so i continued to use it. Eventually, i didn’t mind the smell, and now i love it. Sometimes i’ll just open my jar to take a sniff.
I forgot tooth dust. When you’re getting your teeth drilled for a filling, that tooth dust smell is quite distinct.
Wow tooth dust, that’s a new one!
Add me to the horse-barn sniffers. I’ve been to the Indiana State Fair every year of my life (since I was just a fetus!), and my biggest thrill was always walking into the Saddle Horse Barn for the first time - low-lit, dusty, long rows of old wooden stalls, and the combined smells of horse, sweat, manure, hay, sawdust, and straw. Mmmm. It’s like heaven for a person who has always loved horses and never been able to spend time with them.
Then they renovated the building and made it the South Pavillion. It’s used for other things during the year, so the smells are no longer steeped into the walls and the stalls. It still smells good, but not quite as good as before.
I like to smell the back of my husband’s neck in the morning, before he takes a shower (it just smells like him).
Puppy breath makes me smile, too. (I used to work at a vet clinic/grooming shop, so I had days where I practically OD’d on puppy breath.)