The 3DS has an awesome multiplayer feature: you can play a game with another person even if they didn’t have the game. Which makes multiplayer a lot more accessible to everyone (despite Nintendo’s friend code system).
And apparently, Nintendo has something similarly planned for the Switch. According to Nintendo of Germany’s PR head, local multiplayer will require just a single Switch game card.
Up to 8 players can play local multiplayer on a single game card on some games. So for example, only one player can have a copy of Mario Kart 8, and everyone can play, but only locally.
However, there is some uncertainty about the translation and the attribution to the Nintendo of Germany’s PR’s statement. Hopefully it can be confirmed soon.
If Nintendo confirms this, it will certainly be a big draw to the console. On the other hand, if this was true, Nintendo probably would have announced it as a major feature earlier this month.