Chuck - The Quiz (an Android app)
Years ago, back in the heady days of Android 1.x in the late noughties, I wanted to learn about Android dev so I built this simple app. Its just a simple DB of multiple choice questions with different difficulty levels and just randomly selects a set of questions each time a user plays. It doesn't do anything else fancy.
It has had a reasonable number of downloads (~25k at this moment) and a solid 4+star rating, but it has now got to the point where its a pain to have to keep updating rating questionnaires and privacy policies for it on the app store, so I have unpublished it.
The walkthrough tutorial of how to build an app like this is all written up elsewhere: https://automateddeveloper.blogspot.com