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.
Probably my answer will not concern what I will tell about the program, but about what I liked about Linux, that there is freedom of action and everything is under my control
My answer is also not on topic, but I’ve always liked orange creamsickles
^^