Odyssey

"The exciting TV electronic game center."

The Odyssey was the very first commercial video-game console, predating Atari's Pong by three years. Developed by Magnavox, it was the brainchild of the legend Ralph H. Baer. While it still didn't used ROM-based cartridges (they would only be introduced four yeas later with the Channel F), each game came in a game-card, which was basically a printed circuit board with jumpers, though you had to open the console and remove it's casing to exchange games.

The Odyssey library is relatively small. One of it's games is a tennis simulator which, due to it's similarity to the later Pong, rendered a lot of money to Magnavox through lawsuits against various other companies. Today the Odyssey is only worth looking into as a historical piece.