While pets, smoke and kids are somewhat of a challenge, nothing is worse than that awful Febreze/fabric softener/dryer sheet stench. It permeates existence itself when used by its victims.
Or incense or scented candles. I eagerly awaited a replacement Kyocera receiver some twenty years ago. When I opened the box, I was instantly able to smell the dead hippie whose jasmine incense exuded from the innards of the poor receiver. Back it went.
And then there was a pair of Spendor speakers (BC1?) that had been stored in some sort of mold garden. The guy said he hadn’t had anything to do with the speakers in 17 years, and yeah, maybe they’d gotten moldy in a closet. Back they went.
Eventually (after a couple of vintage receivers that died quickly), I gave up on used equipment. I’m not as audiophilic as most of you, listening mainly now on B&W computer speakers to my own CDs ripped to hard drives 90% of the time. I have tinnitus now, too, so nearfield is nicefield.