2. Heavy Air
A really cool physics demonstration using hexafluorid, a heavier than air gas.
I can't remember if I've posted this before or not. Sorry if it is a repeat. It is a pretty long video of Vova Galchenko, one of the world's top rated jugglers, doing some amazing stuff. Check out the five club transition to behind the back, about 1/2 way through the video, just after an appearance by the KGB.
A "short" account of an incredibly specific area of Lego building block history, the Lego Castle.
Keep a bunch of sheep and knights and scorpions and other stuff from making their way around your yard by shooting them with arrows, cannons, water ballons, fire bombs and whatever.