https://www.jpl.nasa.gov/edu/teach/activity/ring-wing-glider...
Haha. Way back in my 2nd year at university (1985!), these were all the rage. Myself and a couple of friends made a giant version out of 6 university calendars. It had a diameter of about 40-50cm. We launched it one day (when the lecturer was facing the board) from the back of a math lecture. The slope of the lecture hall was a gentle 20 degrees, slowly tapering off towards the front. Initially it cleared people's heads with a few cm to spare, then about halfway it was clearing the backs of chairs - fortunately there were quite a few rows from the middle to the front with no one in them - until it finally found the back of some poor guy's head sitting in the 1st or 2nd row. The ring clunked him square and he ended up wearing it. We all exploded in laughter. It wasn't aimed at him mind - he was just in the wrong spot at the wrong time. I still smile when I think of that (does that make me a bad person?).
EDIT: got the year wrong (memory is fading...)
The other was a plane made with a drinking straw and two paper rings. It always flew really far also!