Beat me to it. That smell dominates my flammables cabinet, along with some type of red axle grease in there. The sulfurs are strong with those two.
Oh, and water snakes.
Bad gas is no gardenia, though.
Oh fuck, I forgot about chicken poop. One Easter, back in college, a roommate brought home four chicks. Then she disappeared, leaving me with the chicks. Chicks grow fast, and they never stop pooping. And the smell is horrendous.
Oh, and I should add: the drainage from a botched surgery for a ruptured appendix and peritonitis.
That’s got to be pretty close to Qadgop’s gangrenous bowel entry.
Gas gone bad will “burn”, sort of, but it leaves glue or varnish like deposits inside the engine. Classic or antique car owners run into this from time to time. It can really ruin your day. I wouldn’t use it in anything I cared about, mixed in with fresh fuel, nothing. In the old school engines it will cause the valves to stick after shutdown. The next time the engine is started, there are 16 nicely bent pushrods. Modern engines, can’t imagine it would be good for injectors. Don’t do it.
I once bought a '65 Chevy wagon full of stuff. And, what smelled like a dead cat.
I paid $25 for the car. It needed a thermostat to run. Sold it to some hippies going to CA for $100.
Man, did that f**ker stink! It was summertime, also. 
The three worst smells I know:
An aquarium infected with cyanobacteria. You know how the scum at the bottom of a pond sometimes gets sulfurous? That’s the smell. Rot and sulfur and putrefaction. I’m sure there’s a bit of cadaverine mixed in there, because there’s a hint of rotting mammalian predator.
A dead sea snail. I don’t know what it is that dead snails reek of more than any other rotting creature, but sea snails have even more of it than freshwater snails, and it’s putrid.
A New Hampshire bog at sunset after a hot day. As soon as it starts to cool they release this overwhelming sulfur stench.
But I’ve never smelled rotten gasoline, so can’t certify to their superior repulsiveness.
**What smells worse than gas gone bad? **
An entire whale carcass that has been sitting in the hot sun on a beach for 10 days, during the process where a team is cutting it apart to get the bones.
I have never seen so many people retching into the bushes.
When I was a youngster we raised chickens/eggs.
Sometimes they would lay eggs away from their nests. And they wouldn’t get gathered. When my brother and I got bored we would search out all the stray eggs. And have rotten egg fights.
Disgusting!
When I was a soldier in the eighties I had a car pool with a guy who one time in midsummer transported a 50 liter milk can on the backseat of his Opel Ascona. Yes, it spilled all over the whole car. I had to ride in that car for several weeks in temperatures of about 90 °F. It was hell and didn’t get any better until in the fall, the Opel’s machine blew up spectacularly on the Autobahn, and that was the end of that stinking car. I’ve much later had a bird rotting in my own car’s engine compartment I only found out about when only the feathers were left, and that was evil, but nothing beat the rotten milk.
You can multiply that number a certain amount if you chop them up first.
Now that I think about it, its the staying power that is horrific. It’s bad, and it just* won’t go away*.
Went to the junkyard and pulled 3 fuel pumps. All leaked horrific shit on me.
I’ll stink till the Forth of July. And then I’ll erupt in flames.
I know you’re not supposed to store potatoes in the fridge, but I’ve heard enough stories about the one that got away that this is why I do.
There’s that classic story about the crew who decided that blowing one up with dynamite was the best way to get rid of it. Let’s just say it wasn’t.
I have worked on/drained gas from a lot of old sat-twenty-years-or-more cars. I also spent a summer as a honeydipper. Leaving a flat of nightcrawlers in Ford Pinto parked in the sun for 10-12 days in August has them both beat on the totally-reeks scale.
Back in my poorer days when my cars had no A/C, I had the opportunity to drive past some chicken houses in the depths south Georgia. In 90 degree heat. A pig farm smells lovely compared to the excrement of 10,000+ chickens simmering in the south Georgia summer!
Not to hijack a perfectly good borderline Pitting of stale gasoline, I figure I’d report the things I learned in my recent research on this factual topic. (Because I’ll fight my own ignorance if I have to.)
“Stale” gasoline is different from “fresh” gasoline by both evaporation of lighter fractions, and oxidation of what remains. Apparently, the oxidation is also what promotes sludging and varnish formation. This seems similar to what happens to finishing oils like linseed: they are applied liquid but harden into a plastic-like varnish after oxidizing.
The difference in smell isn’t explained in any of the sources I’ve read, but I’ll take the amply-attested word of other posters here as good.
We now return you to your previously-scheduled thread.
My landlord once spilled a diaper bucket full of heavily used diapers down the stairs. Easily the worst thing I ever smelled in my life.