Of course
- Accrescent: Store
run(edit: advocated) by the GrapheneOS team for third-party apps - Aegis: 2FA TOTP code generator
- AirGuard: Scans for persistent AirTags in the vicinity, notifies if I may be victim to AirTag tracking
- AntennaPod: Podcast manager, also supports importing local folders of podcasts
- AudioMonitor: Measure sound level
- Binary Eye: Support for many types of 1D and 2D barcodes
- ByeDPI: routes internet traffic through the DNS port to bypass certain types of filtering
- Canvass: doodle app, useful for mid-conversation diagrams and clarifying things visually in the absence of pen and paper
- ClassiCube: Minecraft Classic clone
- Conversations: XMPP client
- Editor: raw text editor
- Elementary: periodic table
- SimpleEmail: minimalist e-mail app that does not automatically fetch linked images. Refereshes in the background every 15 minutes and sends notifications without need for Play Services or equivalent
- FakeStandby: for edge cases when I want something to keep running in the foreground, but don't want to keep the screen on
- Feeder: RSS client
- Fintunes: Jellyfin client optimized for music
- FlorisBoard: customizable keyboard
- Fruity Game: Suika but with MS-Paint art style
- Graph 89: Graphing calculator emulator
- Invizible: Tor and DNS client
- Kiwix: Offline Wikipedia (you can download just the parts useful to you, e.g. medical articles without storage-hungry media files)
- Lemuroid: GBA emulator
- LocalSend: instant P2P filesharing over WLAN
- Markor: notes app with markdown
- Material Files: files app with SMB share support and various handy features
- Molly: Alternative Signal client
- Fossify Messages: I use it over the default messages app since it is easy to block numbers by pattern
- Notally: notes app with nice checklists
- Open Camera: as easy to use as the regular camera, but with a bunch more features below the surface
- OpenContacts: saves contacts as individual .vcf files to a directory for easy backup and allows dropping unknown callers without bothering me with a notification
- Organic Maps to be replaced with CoMaps later
- OSS Document Scanner: best FOSS scanning app I've found so far. Includes auto-cropping (given enough contrast) and adjustable B&W filter to eliminate off-white background colors.
- phyphox: view output of sensors like the barometer, magnetometer, accelerometer, etc.
- PipePipe: NewPipe but better (except for the occasional memory leakage)
- QDict & QuickDic: offline dictionaries and bilingual wordbooks
- RadioDroid: IP radio client. Can tune in to international news, music, sports broadcasts
- RHVoice: TTS app
- RiMusic: NewPipe, but for
Spotify, etc.YT Music - SecScanQR: QR scanner and generator with history, useful to save QR addresses for later use since I don't want to fill out forms or read documents on my phone
- SuperTuxKart: the only [edit: other] game on my phone
- Symphony: Music app with a slick UI
- Trail Sense: Compass with various goodies useful for outdoor activities
- Breezy Weather: weather app and homescreen widget with a slick UI
- MicroMathematics: Math engine, but I never learned how to use it