For me, it was perhaps simple-scan, a very simple and efficient GUI to scan documents. I used it with my Brother printer / scanner and it works like a charm. Especially since I do not scan stuff often, so a program with more complex UI would have the effect that I forget how to use it until the next time.
The media integration is great. I can comfortably pause videos I’m watching from my phone’s lock screen. And it does it automatically when a phone call comes in.
And I can use it as a remote mouse and keyboard. That was the first thing I used it for when it was just a small app some guy created for their own needs.
And the clipboard synchronisation is also sometimes useful to get links or so from one device to the other.