- Circle or Polygon? Scott Farrar. This thing is poised to take over the all-time list once it crosses the 25-response threshold.
- Lemonade, Christopher Danielson. On some other site — let's call it Bizarro 101questions — Danielson uploaded a video in which he dropped a can of concentrate into each of those containers and started filling them with water.
- Megalodon Tooth, Jake Jouppi. I know I declared a moratorium on this kind of imagery (which is all over the site at this point) but think about the size of that shark, okay?
- Ping Pong, Bob Lochel. Great first act with strong implications for the third.
- Roller Coaster Steepness, Tom Ward. An excellent supercut of roller coasters that asks the student to first decide which one feels steepest (that's a low rung on the ladder of abstraction) before using mathematical analysis to determine which one actually is steepest.
My own listings:
Median photo perplexity: 46.
Median video perplexity: 51.
Photos own the top ten list but videos are more perplexing, on balance.