I've been using AntennaPod for years now to listen to podcasts. It works great and feels like a premium app.

Aves Libre is a nice photo app

CoMaps with Sherpa Onnx is an amazing combo for a map app that tells you directions verbally

Grayjay is great and also the only open source app to my knowledge to watch and download Rumble

Mupdf mini
https://f-droid.org/packages/com.artifex.mupdf.mini.app

Voyager
https://f-droid.org/packages/app.vger.voyager

Irregular Expression keyboard
https://f-droid.org/packages/mf.asciitext.lite

Feudal Tactics
https://f-droid.org/packages/de.sesu8642.feudaltactics

Some overlooked ones:

Material Files

Anx Reader

Overmorrow Weather

OSS Document Scanner

Lavender Photos

KashCal

Pipepipe (can filter out shorts)

OsmAnd (keep your points of interest locally, 3D hills, satellite maps, update your area if not on map)

Alarm Klock (I have tried many others too)

QuickWeather (forecast, radar, Open-Meteo)

NeutriNote (notes)

Arcane Chat (deltachat client)

Idle Fantasy (occasional game)

GCompris (kids educational games)

SicMu Neo (tight music player)

Equate (unit conversion app)

Aegis since I was extremely, extremely annoyed that Google authenticator added entries by order of appearance, had no search, couldn't reorder them, and just blasted your numbers publicly with the app open.

Aegis has all of that... These are just basic features...

Canta, can get rid so much slop right off the device without a laptop and adb. Then you can get rid of slop they slip in with updates.

I've been using Episteme Reader on my tablet for ebooks. It's been working very well so far.

https://f-droid.org/packages/com.aryan.reader.oss

Seal. I started saving videos that might go dark.

Phocid music player. OpenScale, roundsync, pulsar are all great apps. There is no equivalent on the play store. These are quality, and do exactly what they need to with no bs.

A large majority of my apps are from F-Droid these days, but here are some of my favorites I haven't seen in this thread yet:

(Note that some of these need the IzzyOnDroid repo installed, not sure if that counts as cheating)

Tempus A rapidly improving music streaming client for Subsonic/Navidrome/Jellyfin

Kvaesitso The best launcher on Android period (Nova users, give this one a try as Nova is no longer receiving updates!)

Lavender Photos My favorite gallery app! Clean, modern interface and some very good basic editing tools that provide utility without making it feel bloated

Breezy Weather A very nice looking weather app that allows multiple weather sources (defaults to Open Meteo)

WG Tunnel A very clean and simple Wireguard client so you don't have to install your VPN provider's proprietary app

LibreTube for watching WC26 at work