I have a ton of assorted ones from over the years. Here's a select few:
Play the Wii Shop Theme when I open the Play Store
Turn on Samsung's built in Protect Battery feature at night, and automatically turn it off when my alarm goes off in the morning
Open Spotify automatically when I connect to my car's Bluetooth
Turn on Silent mode when I get close to work and disconnect from my car, and turn it back off when I reconnect to my car's Bluetooth
Set my AoD to Tap to Show when I have no notifications, but change it to Always On when I have notifications from apps I mark important
Track my earbuds' battery life via a persistent notification when they're connected to my phone
React to double tapping volume up when not playing media to toggle the flashlight, and ditto with the volume down to open the camera
Clear persistent system notifications that I don't want or care about that otherwise normally won't let you clear them or turn them off (take that Google)