[NoodleIncident]

It basically plays audio files. I've played most of my Odyssey playtime with just the joycons by themselves, no strap or grip, which makes it more noticeable. Top 3 rumbles:

1) The "fizz" when you're swimming in a carbonated sea

2) Rumbling motorbikes in the city and elsewhere

3) The scrabbling feet of a "Jaxi"

These aren't the only things with rumble, just the ones that I thought felt most unique. I've also heard that in Mario Kart, the sound of picking up a coin is essentially played by the joycon's rumble, even when the audio is off.