The foxhole radio was very popular during the second world war to keep up with news. It has no power source as it gets it signal from radio waves. The safety razor and lead from the pencil act like a switch by moving the pencil lead across the blade you can hear radio broadcasts.
Supplies you need:
Safety razor blade
Look at the image above to see how to create the foxhole radio.
Also, take a look at this video to get instructions of how to make the foxhole radio.