Bathroom ceiling light. Turn the switch on, turn on all the bathroom ceiling lights, and turn the switch off to see which one it works. Then leave that particular light's switch (on the fixture) in the on position and you'll be able to operate it with the wall switch.
The wall switch is both to help serve as a reminder that the light is on, as well as let you know when the bathroom is occupied.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR