You know a science demonstration is going to be good when it contains the line, "Ask an assistant to light your hands for you." I can't tell you how much I wish I had access to a classroom chemistry lab right now. And chemistry students? Ask your teachers to do this for you to test their mettle!
I like to think that, in many ways, I have moved on since childhood, but I never have gotten over bubbles. That's why I'm a little angry that I didn't think of this myself back when I had access to places with bunsen burners. All it takes is setting up the gas valves for one of the burners so that it blows into a tube of soapy water making bubbles. The bubbles form, with the first few filling with the air in the tube, and the rest full of methane.
Methane's lighter than air, so when it's filling the bubbles, they don't droop down over the side of the container. Instead, they rise in a nice column. When they're freed, they go floating upwards. I would love to see the poor assistant in this video, hunting down the floating bubbles of death with a lit match. It would be even better in a clear field.
The oils on our hands break soap bubbles, which is why it's necessary to coat the hands with a thick solution of bubble liquid. The methane bubbles adhere to the liquid, but don't break. Light them up, and you've got a column of fire rising from your hands. Awesome!