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.
I use zoom several times a week, and have had to revert to windows several times because development lags behind win/mac, and for some reason my org has a fixation on trying new features, useful or not.