I have an olfactory compulsion which you may find weird. Perhaps deviant. Here goes:
I love the smell of a freshly-cleaned primary fermenter. But not just any primary fermenter that's been rinsed and then shown the PBW (I may be deviant, but I still have standards): it depends greatly on what just got cleaned out. A hoppy American ale fermented with 1056? Heaven. A dark lager brewed with WLP833? Seductive. British strains? Meh. Non-Brett Belgians? Not so much.
That scent ... it's beery but clean, with suggestions of a cold oven after the bread is baked, hops and CO2 echoing in the nasal cavity. Sometimes on a brewery tour I'll catch a whiff of it near the conicals or the bright tank and wander off ... Am I on my own here? Anybody else? Stand up, we're among friends. There's no shame.
And I know a whole lot of you sniff airlocks.