Clean sheets does it for me. I love crawling into bed after a long day, and smelling cool, crisp, clean sheets.
Since we’re including people taking showers, I’ll have to say a baby washed in Dove soap is the best clean. Nothing better than a clean sweet happy baby sighs. Wish they wouldn’t grow up so fast…
There are a few levels of clean:
BABY-CLEAN: Johnson’s Baby Wash and Baby Powder along with the natural newborn-top-of-the-head-smell. Pure heaven.
WASH-CLEAN: TIDE™ washed clothes line-dried. Any clothes line dried smell and feel better to me than any Snuggle-inspired dryer nonsense. Even line dried towels in November. I’d rather have the roughness and the great smell than softness and “April-fresh”. But, that’s just me.
DISINFECFTANT-CLEAN: This is LYSOL. My mother used LYSOL, the original brown bottle LYSOL, on EVERYTHING. Sheets, counters, floors, etc., when we were sick or not. Clorine smells like tap and pool water to me; ammonia smells like jewelry polish. LYSOL was (and still is) the disinfectant of choice in our house. Works great on well-used New Balances washed in hot water.
We are queens of clean in my house! 
I’m not a clean freak despite my username, but I’d say a slight bleachy smell means clean to me. My nose thinks a strong bleachy smell means sanitized. Fern Forest reminded me that the cold smell after a big snowfall in the country is a good clean smell too.