Droid-ify is a much nicer client for F-Droid.

Obtanium for downloading apps from various other sources.

Aurora Store for anonymously downloading apps from the Play Store without a Google account

LibreTube or NewPipe for watching YouTube videos without ads or tracking.

Seal for downloading YouTube videos.

Retro Music Player - probably the best looking music app for Android.

Pano Scrobbler - a FOSS app for Last.fm, Libre.fm and Listenbrainz. (I recommend Obtanium to download it from GitHub.)

Murglar for downloading Music in full quality from Deezer.

Molly - a better Signal client. (You can use Obtanium to download it from GitHub, you can add their F-Droid repo or download it using Accressent, a new experimental app store that seeks to replace F-Droid.)

Gallery - a simple gallery app that looks good and respects your Material You theme.

Element X is a much better Matrix client than the standard Element app. (I recommend downloading it from GitHub using Obtanium.)

LinkSheet - a small app that restores the old Android URL link chooser. It has many great features like the ability to remove tracking parameters from URLs or using FastForward to annoying bypass URL shorteners.

UntrackMe - a tool that can redirect YouTube, Twitter, Reddit, etc. links to privacy-friendly alternative frontends like Invidious or Piped for YouTube, Nitter for Twitter and LibReddit or Teddit for Reddit

Thunder, the best Lemmy client I ever used.

Most of the apps I mentioned are free and open source and many of them are available on F-Droid. They don't collect or sell any of your data.

The last one is not an app, but an entire OS that can replace the spyware-infested ROM that's preinstalled by your phones' manufacturer. I'm talking about GrapheneOS. No ads, no tracking, no proprietary Google services. Just free and open source software with maximum privacy and security. It's so great!

https://play.google.com/store/apps/details?id=name.boyle.chris.sgtpuzzles

Several puzzles in one app, no ads, completely free.

Physics Toolbox Suite.

Most phones today contain a powerful array of sensors, and almost all of them are locked from easy access by the user. Physics Toolbox has functions that allow you to get the raw data from almost every sensor in your phone. It's the only "tool" app that I can honestly say I've used as a tool. It has a sound intensity functions which I have used to determine if hearing protections is needed, and I've used that feature to diag a bad mic pickup due to an ambient white noise machine. It can give you the signal loss for a WiFi connection, very handy for troubleshooitng wireless access points.

Other features, magnetic field detection, tone generator, color matcher, g-force and rotation output, raw GPS view and more. All of these are available on the free version, but I actually use this app so much that I sent the 2 or 5 bucks to the dev mainly just to support them. The paid version also lets you export the sensor logs to a .csv file so you can view that data on a computer.

It really turns your phone from a glorified Lemmy portal into the cool future tool it was meant to be.

Games:

Survivor.io - even though the name screams cheap shitty ad app, it's pretty limited in ads (if any) and the game is a rogue like zombie killer. Each game plays out for about up to 15 minutes. One of my favorites.

Rebuild - a turn based strategy game about surviving the cities full of zombies.

Pawnbarian - a chess rogue like where you control a piece that has unique abilities. I believe they let you play part of the game as a demo.

Lifeline - a game you can get where you text some random dude who is lost in space. The game progresses over a few weeks and unfolds but you can only message him after he contacts you through notification.

Apps:

Nova Launcher - I have used nova launcher for probably like 10 years. I love the customizable options given and the ability to set gestures on icons.

Doctor on Demand - OK HEAR ME OUT. First, I live in America. Medical care is stupid. Also, I have children. Going to the doctors is like upwards of a hundred dollars per visit (if not more). Doctor on demand (through my insurance) is free. Even if you don't have insurance, I think it's only lope $50-$75 per visit. So.. I recommend this for American users who need to see a doctor but may not be covered effectively.

Offline Survival Manual - haven't needed to use it but good to have I'm thinking. You can print it all out through the app.

https://www.f-droid.org/packages/de.westnordost.streetcomplete/

StreetComplete! You can contribute to OpenStreetMap while walking around and having fun. It's super fun and satisfying to unlock achievements while contributing to a useful project.

Radio garden

This lets you connect to a lot of stations across the globe, by moving the globe

NeverTooManyBooks.

I have several books cases and shelves where I store books, this has helped me a lot to have a catalogue of them.

I just scan the book code, the app gets book info, and I assign it to a place where it is physically stored, like, bookcase 1 in office room, shelf 3 on main room, etc.

I have it installed from Droid-ify which is like an app to have more sources for f-Droid.

https://apt.izzysoft.de/fdroid/index/apk/com.hardbacknutter.nevertoomanybooks

URLCheck

Checks URLs for nasties like tracking links. Can also be used to open links in specific apps (where they don't always want to)

Available on both f-droid and the play store.

https://www.f-droid.org/packages/com.trianguloy.urlchecker/

https://play.google.com/store/apps/details?id=com.trianguloy.urlchecker

Atomas is a lovely little game about atoms.

X-plore file manager. I've been using it since UIQ days.

If you are not streaming music, but play your local library - PowerAmp.

Accubattery

Minimalist Phone has changed my life. For anyone looking to either spend less time on social media or get rid of the digital clutter constantly bombarding you, this app is amazing.

It Filters my notifications so I can check them on my own time, it sets time limits on all social media and game apps and kicks you out when time is up, and it has a simple black background with no app icons, only the names of the apps you choose in white letters. Perfect for my over-stimulated adhd brain.

URLCheck

Simple Text Editor

FOSS text editor for when you just literally wanna write something down without any weird bloat and without having to deal with Google. Available on F-Droid.

Also, OpenBoard for a FOSS keyboard with swipe typing. Also available on F-Droid

You know what, I think F-Droid is actually my hidden gem app. I'm sure most Lemmy users use it, but I don't think I know anyone else IRL who does, so hidden gem might not be accurate depending on perspective.

I'm not so up on what's new and such, and I've really enjoyed a few games I've downloaded:

(Obligatory apology for any link or format issues. On mobile and first time posting.)

Scalak. You rotate and move blocks and pieces around to try to match up edges. Hard to explain. Kind of like the baby's "put the square in the square hole" toy except for adults. It's got really nice, calming music, so it's nice to play before bed or offline on the plane.

MultiSudoku. Off-line sudoku that has five sudoku squares (?) attached together.

Word Hero. I love word games and this has been my favourite. It's basically Boggle and after each game, it ranks the scores from everyone around the world who played the same game as you. Been playing this for years. Unfortunately online only.

Burnable Garbage Day. Earth has completely filled with rubbish, and a cleaning robot has woken up from a deep slumber to find out why the planet has become this way. Originally a Japanese game so the translations are a bit dodgy, but it's a really fun play. I think it can be played offline. It's been a while since I've played this.

Mahjong 13 Tiles. The only actual mahjong game I could find that isn't like the old Windows tile matching game. This is the gambling version where there is no money bets, but you can play against bots. It's been ages since I've played this so I can't remember if it's online or offline or if you can play against real people.

Dingbats. Guessing famous idioms from drawings. Can be played offline.

Quell Reflect. Moving a bubble around to capture all the gems. The puzzles get harder as you progress. Can be played offline.

Influence. You start with one cell (think Chinese checkers) and you keep spreading your influence to conquer the other players. Can be played off-line.

What the Forecast. Obnoxious, rude weather app.

Whicons. Minimalist white icon pack for Android.

BirdNET. Identifies birds by their call. I've used this in Canada and Australia.

Plant Net. Same thing as BirdNET but photos of plants. Also can confirm it works in Canada and Australia.

Edit: Forgot one game, Slitherlink. I set it to easy and listen to podcasts in the background to wind down at the end of the night. Each hexagon (or whichever shape you choose) has a number, and each number represents the max number of sides that can be selected. Eventually the entire board is connected via one line. You'll have to read the description, it's the best description I can give, albeit not a very good one.

Edit edit: This is what happens when I haven't had my coffee yet. Kakuro is another numbers game like sudoku.

This calculator app maybe I use it for nostalgia's sake but I've had it on every android for the past 10+ years. It works great, launches instantly, and the ads were never more than a small banner at the top. I did buy the ad free version but it's $2, no subscription or any bullshit, just a straight and honest scientific calculator.

Maybe not underrated because everyone should already be using it but KDE connect is a life changing app. So much functionality packed into a lightweight package. Just having a shared clipboard between my phone and laptop has been such a time saver every single day. If you don't already have it, you should.

-Organic maps

Beautifully designed open source navigation alternative. It's not perfect, because I still have to do some auxiliary searching occasionally, but I'm really enjoying using it instead of Google

-Quickweather

Another beautifully designed app. Not perfect, but just really nice to look at because of how well it was done. I still use myradar as my main driver, admittedly.

-ViMusic

Again, one of the most beautifully designed apps I've ever seen. It has a few bugs, but I really enjoy using this one. It uses YouTube music as the back end.

-Newpipe and freetube

Either of these work pretty good as a better way to watch YouTube videos. I'm glad people are fighting back against Google's bullshit...

-Eternity

This is currently my favorite Lemmy front end. I've tried many so far and this one seems to have the best functionality and customization too.

Leafsnap - an excellent plant identification app. Can id from a photo of a flower, leaf or bark.

ArityCalc is really neat, does graphing and a few other things

JRPN 16C is a take on the HP 16C , it's both fun to mess around with and a great help when working with raw memory

μMath+ is great for working with complex problems

I use a NewPipe fork called PipePipe that is a bit more stable from my experience

Aurora Store is great

Markor is my go-to notes app, lets you write notes in markdown among other things

Trail Sense is neat both for its intended purpose as a general hiking toolkit, but also as a way to check phone sensors

Total Commander, because of course

Organic Maps is an offline maps app based on OpenStreetMap data, it's great

Niagara is by far my favorite launcher these days

I use it with Frequaw as the only widget to launch the apps I use the most

I rue the day Identiconizer falls behind on API versions and I won't be able to install it on new phones anymore. Having identicons for contacts I don't have photos for is just so much nicer than the plain letters.

Living Worlds has gorgeous low-power animated wallpapers

AlmostTI stops me from needing to learn how to use a newer calculator than the TI-84

Dope Wars Classic. The best modern recreation of the TI Calculator/Palm Pilot game Drugwar.

Still awesome to play to this day.

Joplin https://joplinapp.org/ It is a free an open source note taking app similar to Evernote. You can keep your data on a cloud service (such as Dropbox) to keep your notes in sync between Android, Windows, Linux and IOS or you can pay for Joplin Cloud storage.

Gravity Screen.

https://play.google.com/store/apps/details?id=com.plexnor.gravityscreenofffree

Screen turns off when you put your phone into your pocket. No more pocket dials etc.

Might not work on newest devices.

Spotiflyer <- Give a link to a song/playlist from various platforms and it will download it for you.

Feeder <- Great all around RSS feeder that can help you read your feeds on the go.

Metro player <- FOSS music player with great customizable UI. Has tons of features.

Probably more that I can't think of at the moment.

Not sure how hidden it is, but I've been using Librera FD for the PDF of the textbook I needed for one of my classes. I only really ever use it for the PDF reading function and the search for certain words function, but it works great for what I need.

I also don't know how hidden it is, but I also like Anuto TD (Another Ugly Tower Defense for Android) has been something I just got back into. It's simple and fun enough to play since it doesn't require too much thought.

FX File Explorer. Super fast, feature-rich, and customizable, free with no ads and tracking.

Localsend - it's like airdrop but for android, linux, windows, and mac.

KISS launcher, I can't imagine using a phone without it.

Quick Cursor, reach the top of your screen effortlessly.

Forkyz let's you download and solve crossword puzzles.

It comes with an inbuilt list of sources for different languages but you can also manually add new ones. Many newspapers publish crosswords daily or weekly for free so there's plenty of options.

Mixplorer, a file explorer that does everything. Want to share a file between android devices on your home network over WiFi because Bluetooth will take a million years ? Start a server via mixplorer, send from mixplorer on the other device. The other day I was looking for an app to browse a simple nas storage. I searched for "nas" in F-droid and found nothing. Then I remembered good old mixplorer. Yup there it was, add smb. And I think I barely use 10% of its capacity. Batch processing, queued actions, regex renaming... Many add ons. Edit:free on xda

Essentials: DiskUsage, Total Commander

Music Folder Player - just a good music player that plays files in a folder instead of scraping all audio files from wherever as many players seem to do nowadays

Syncthing - to sync files with other devices

Fit Notes - simple lifting progress app that i've been using for years. On play store.

Kvaesitso - launcher on fdroid. Has become my favorite launcher.

Consider crossposting to !askandroid@lemdro.id

Is newpipe a hidden gem? It was to me until 6 months ago.

I put Trek: Total Interface and Total Launcher on my phone to replace the normal Android interface and for the first time in fifteen years I like hearing my phone make noise!

They work really well on my pixel 3 and respond much faster.

Did no one mention Flush yet?