From the F-Droid website:
“F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.”
For the reasons outlined in Why self-host/use FLOSS?, using FLOSS (Free/Libre and Open Source Software) whenever possible is preferable. The source code is available for every app on F-Droid.
ImagePipe or Scrambled Exif. Both apps are designed to remove EXIF data, metadata in photos that can betray personal information, before sending pictures. Despite serving a similar purpose, the two apps differ in implementation and in terms of features. Notably, ImagePipe also reduces image size (though it keeps the original unaltered and stores the changed copy in a separate folder), which may or may not be a desirable feature depending on use case.
KISS Launcher. I find that pinning a few choice apps and searching for the rest with KISS Launcher is a more pleasant experience relative to the default GrapheneOS launcher. Also, launchers allow one to use custom icons (I use Arcticons Dark).
Meditation Assistant. Practice agnostic and doesn’t do more than I need it to–in other words, perfect for my use case.
mpv-android. For those that love mpv and want it on their phone, too.
Netguard. Block access to the internet per application. Unfortunately, I haven’t found a way to combine it with Orbot yet.
NewPipe. NewPipe allows the user to watch YouTube privately on their smartphone; in addition, the user can keep up with their favorite content creators without signing up for an account.
Orbot. An invaluable tool for privacy, Orbot tunnels the traffic of selected apps through Tor.
RedReader, an unofficial open-source client for Reddit. It has a clean UI with no nonsense. I found it through word of mouth, as I’ve never liked the redesign and wanted to find a less feature-rich (and frankly less buggy) client than Slide. This is exactly what RedReader provides.
Termux. Termux is a terminal emulator for Android, and offers an incredible amount of power. I use Termux to securely transfer files between my smartphone and computer using SSH.
Yet Another Call Blocker. Quite a useful app. Problematic area codes can be added to YACB and it will filter them out automatically. Contacts can be exempted from being treated as unknown callers, and YACB even has an option to stop the call before the phone starts ringing on Android 7+.
UntrackMe. UntrackMe transforms certain links, such as YouTube, Twitter, and Instagram, to point at a FLOSS privacy respecting alternative. In the case of Twitter, it changes the domain to a Nitter instance, for example.