A mouse that can only charge if placed upside down, or in rare 3rd party charging carriages. Apple making things nice, neat and simple as they usually do.
That was one of the main reasons why I sold my Sony headphones and replaced them with Airpods Max. Charging the headphones while in use isn’t really any more inconvenient than using wired headphones would be.
My Sonys can't be used with Bluetooth when charging but you can use 3.5 mm audio input so they act like wired when charging. Probably because they're using a fairly standard Bluetooth chipset which also controls charging
To be fair, I charge my Magic Mouse once a month and it takes less than an hour. Throwing it on the charger overnight when I leave for the work day isn’t a huge deal.