Rear projection TVs have several useful items inside, but the best one is the large Fresnel lens, which is basically a giant magnifying glass.
Candles are the easiest lights to synthesize in an emergency situation. Some of them even double for cooking and heating purposes.
7 Trumpets Prepper recorded a video where he shows step by step how he build a custom bicycle generator. This would be a great thing to have.
Sensible Prepper made a great video tutorial on how to make a penny can stove. This contraption costs next to nothing to make, and it’s very efficient.
I found a great video on how to build a rocket stove using only 16 bricks. I had heard about this method but had never tried it.