The Atari Channel
One of the most amazing qualities of the Atari home gaming console was the fact that NOW you (ordinary joe) could put your own programming on the TV and interact with it. Attaching a special "adapter" on the back allowed you to jailbreak (if you will) the regular channel 3-4 programming and input your own.
Now you're not just watching the TV, I'm putting stuff on it, cool interactive game stuff.