Great question! There are so many but there are two tied for my favorite.
One was about urban gardening. The guy was from Los Angeles, Compton I think. He said something like, "Growing your own food is like printing your own money." I don't print my own money but I started growing some tomatoes on my balcony last summer.
The other wasn't long. The guy taught viewers how to dry their hands with only one paper towel. Only one! Spoiler alert: after washing, shake your hands 12 times, then use only one paper towel. Too easy!