All of Wikipedia on your device (if you have 80GB available)
There’s a really cool app called Kiwix, that can read .zim archive files. With this app, you can download and use an archive of Wikipedia, to be available when you’re not connected to the internet. There are also a ton of other archives out there, like Wikiquotes and the Game of Thrones wiki.
You can download the Wikipedia archive (78GB) from Kiwix, but I had better luck getting it directly from dumps.wikimedia.org.
This app is also available for Android, Windows, and MacOS. (edit)
I use it when I’m camping or traveling for extended periods in the country, where I often don’t have easy access to the internet. I have it on my iPhone and my iPad.
What a time to be alive!