Wooden match, head removed, needle at one end and tiny cross fins in the other. They’d stick in the ceiling every time and have to remove with a broom.
We used to take the soft butter pads in the lunch room and lay them in the middle of the napkins. Let it hang down and pop it by pulling. Those would stick on the ceiling in warm weather and drop on the next lunch bunch or people eating. We also stuck the plastic milk glasses on the underside of the dining tables. When the weather got hotter, they would start falling off.