The inverse of this thread
Coffee
Vomit
Skunk
Vomit
Cheese (often interchangeable with the above)
Fish
hard boiled eggs
sewage
dirty socks
People who think they smell good because they apply scented products to their bodies, to mask what they really smell like. Actual smells of people are really pretty cool, because they often are influenced by what they eat or other aspects of their living circumstances. I’ve been on crowded transportation in a dozen countries from Moldova to Cambodia in the past year, and the only people I encountered who smelled bad were the ones who got their hands on a bottle of Old Spice.
When I was in high school, a lot of my farm classmates came in on the bus in the morning, straight from doing chores. They smelled like Barn. Which was cool. I still have the memory of it.
Tobacco smoke
Weed
Hot concrete that’s just been rained on
Yankee Candle and Bed Bath And Beyond stores
Cat piss
Propane (I THINK it’s propane; it smells like soggy white bread, and I’ve only ever noticed it where people have bottled gas in use)
Stale air inside a car tire
Decaying animal.
I found a Raccoon stuck in the deck of my riding mower (I didn’t run over him - he must have tried to hide in there and got stuck). He’d been there for a week or so, and…the…smell…
Oh My!
Hee, I like all of these except the cat piss. Different strokes 
Anything resulting from the action of anaerobic bacteria.
B/O - there’s a guy in the office…ugh… I have to wait 10 minutes if he beats me to the coffee room in the morning.
Clove.
Stale coffee and cigarette breath, combined
Rotten lettuce
Dissected bowel
I think I was going to vote this too but my case may be aerobic for all I know. Coming back from vacation I didn’t clean out my cooler or bear barrel for around a month and when I got around to it they both stank too much for me to even throw the contents out. I assume that there wasn’t a lot of air exchange since once I put the lids back on I could keep them in my apartment without smelling them. Then, just this month, after almost a whole year I got the courage to open them again, and the cooler simply smelled like must and the bear barrel smelled like maple syrup (!). The bacteria must have eaten everything available and then the resulting smell must have slowly leaked out.
Patchouli. I hate it so much.
Tonsilloliths
The gunk on the floss after I floss my teeth 
Canned, wet pet food
Rotten potatoes.
Dead mouse or squirrel, putrefying, under your floor or inside the walls, where you can’t find it or get to it.
Carrion flowers (of which there are several).
Gardenias.
Anything produced by anaerobic bacteria.
Halitosis.
Combined, concentrated, artificial floral/plant/food scents (that smell that hits you when you walk into a Bed Bath & Beyond, candle store, Bath & Body Works, etc.).
I used to include coffee in that list, but something happened to me in my 20’s and I began to love coffee.
The smell of cooking eggs.
I loathe eggs. I can barely stand to watch a commercial for an Egg McMuffin. On those rare occasions when Ivylad cooks himself an egg, I have to leave the general area.
City landfill. Nothing worse than rotten vegetables of all kinds.
Stinky tofu
I don’t know if there’s a name for this, but what a 70 year-old chain-smoking alcoholic that hasn’t bathed in a week smells like
Hippies
Landfill leachate.. “strongly odoured” says Wiki, world’s biggest understatement, like saying Hitler was “A bit of a dick”
Fresh concentrated skunk spray.
Dead rotting skunk.
Pickles, or anything pickled.
Old person smell. I read study once that said people liked this scent. I don’t believe it.