The Game&Watch were not only sold in boxes, instead some of them were released as blisterpack as well. It's not known for sure how many different ones, but it's about 30 games. Game&Watch were released as bliserpack from the following series: Wide Screen, New Wide Screen, Multi Screen and Micro vs. System.
Yesterday a Zelda blisterpack was sold on eBay. The price of about EUR 283.- is no surprise, because blisterpacks are very rare. Link to the auction