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.
Back then CS:GO used to run better on Linux! That was why I switched (apart from a borked windows system I put Linux on just for shits and giggles): to get more frames, lol. Now I couldn’t live without Linux, even though I don’t even play CS:GO anymore.