I created an online game to learn the names and faces of people in the office while I interned at IDEO. When I was coding, I thought of it as a practical tool. It's awkward when people know my name, but I've forgotten theirs.
Then something strange happened.
I showed the game to my mom and she enjoyed learning the names of people that she's never going to meet. I heavily discounted this, but figured it couldn't hurt to share the game with the rest of the office. I was surprised that people spent a lot of time playing (some over a half hour), even though they already knew each other's names. People have recommended more use cases than I could have imagined for something so simple.
For some reason, a simple flashcard game is fun when it involves faces.