Android: Wikipedia's barebones Android app hasn't been updated in a while. If you're looking for an alternative app with more features, WikiExplorer improves on the basic functionality of the official app and makes reading Wikipedia an enjoyable experience.
One of the most standout features is the ability to create reading lists. When you go down the Wikipedia rabbit hole, it's easy to come across dozens of articles you want to read later. Reading lists allow you to sort and organise them for perusing at another time. The app also repeats some functions that the stock Wikipedia app does, but it does so in a much more intuitive way, allowing you to save articles for offline reading and find articles based on your location.