I spent two years of college in a dorm room with a sink (and no other plumbing). I mostly used it for brushing my teeth and shaving, though slight laundry was also possible. Could also use it for various minor cooking tasks (which I think weren’t technically allowed, but everyone did it).
Reef aquariums. There are many stories in aquarium site of people getting visits from law enforcement because of the type of lights they buy online. And they tend to keep them on the slab due to weight and well insulated so the critters don’t die in a blackout.
Many hotel rooms have the sink in the room with the bathtub and toilet behind the door. That way one can brush one’s teeth while another is showering or using the toilet.
Edited to add, that is in response to @Chronos.
My first dorm room, in 1983, was also like that. You could wash your hair in that sink, although it was tricky, and it designed for that and personal grooming (and puking in if you were hungover and couldn’t make it to the bathroom, although I personally never used it for that).
Japanese homes have the toilets in separate small rooms.
I don’t remember exactly, since is was so long ago, but my university residence was single-bedrooms with jack-and-jack 
sink / mirror. Since (boys) we rarely used the mirror for anything, there was never any conflict.
My own garage. It’s a very nice 4 car job.
The previous owner hung a ceiling fan in it. Not weird, but it’s practically a chandelier. I think it was repurposed from somewhere else in the house when it was replaced. The previous owner was a tee-shirt screen printer, so I can see why he wanted air movement in there.
It makes me chuckle to park under a chandelier. I mean, that’s class (?)
Police monitor what kind of lights people buy online?? Don’t they have anything more important to do?
A house I lived in as a child had the living room, kitchen, etc, on the first floor, bedrooms on the second floor — and the third floor consisted entirely of the only bathroom in the place. Not sure why the architect decided to make that the hardest room in the house to get to. Definitely a home suitable only for people without mobility issues.
Some relatives on my dad’s side lived in an old Victorian house in a little farm town down the road from Springfield, Illinois. The main bedroom had an attached bathroom – with no wall. It was kind of around a corner in a way (it’s hard to explain), so there was visual privacy (no one could see you) but no audio privacy – everyone could hear what was going on in there.
Their two daughters loved to poop in that room for some reason.
If they’re looking for clandestine marijuana grow-houses, yes, they do monitor this.
I’ve spent some time in some old farm houses that were build haphazardly. The weirdest one wasn’t a room - it had a rear entrance that opened up to the landing between flights on the stairway, in other words between the first and second floor. Which wouldn’t be so weird if it were on a hill, but it wasn’t. You had to take a stairs up to the landing doorway.
Then, they took out the outdoor stairway when they put in their pool. They still kept the outward facing door, though, that opened to thin air. They taped it shut so hopefully no one would open it by mistake.
The farm house I lived in had two bedrooms upstairs, and an incomplete third bedroom that I think they just never got around to putting in the fourth wall for. It was the right size for a bedroom and even had a closet, and was located a ways away from the stairs so it wasn’t a foyer-sized landing. We used it as a playroom / work room. (But the house with the door to nowhere did have a foyer-sized landing, which wasn’t used for anything.)
A third farm house had a manually built extension that was a bathroom and utility room, but in one large unseparated room. The toilet faced the door, so you couldn’t even hide if you were using it.
But just in this thread I realized the weirdest part about it. I visited that house during the early 80s, and the addition was quite obviously very new. And here’s the part I didn’t realize: it was the only toilet in the house. I never saw an outhouse at the property, but the implication is obviously that it had an outhouse until some time in the 70s.