The crystal radio
Another one of my favorite childhood Christmas presents was an early-1970s crystal radio set. It was a simple plastic box with a simple mechanism inside. Some assembly required. It weighed practically nothing. I used it to listen to hockey games broadcast from the old Memorial Gardens ice hockey arena downtown, which was actually only a few blocks from home. But the radio's power was so weak it felt like I was listening to messages received from the cosmos. I didn't understand crystal radios at the time, but I do today. They require no external energy source, but are powered just by the energy of the received radio waves, which explains why the signal is typically so weak. It was a lot of fun at the time. I dared to climb up onto the roof of the house to string up a long wire antenna for better reception. I don't know if it worked, but climbing up onto the roof was a thrill, and it made me feel like I was accomplishing something.