VLC is a big one for me.

Organic Maps

Damn near every tool I use on PC, really. Audacity, OBS, VLC, all the random bits of software I need to run my jank-ass FBT setup…

7zip

Practically every single FOSS application I use is highly useful to me, and of course, free, so I’ll just list them all here.

• Immich - A full-featured replacement for Google Photos, has a sleek UI, face detection, albums, a timeline, etc.
• Paperless-ngx - Document management system, saves me a ton of paper hoarding, and makes everything easily searchable with OCR.
• Syncthing - Simple file synchronization between my devices, on my terms. Doesn’t share data with big tech companies about my files, and hooks up extremely fast P2P connections that beat cloud-based services by a long shot.
• Metube & Seal - Simple interfaces for downloading with yt-dlp, can download from YouTube, but also many other sites. Doesn’t spam you with popup ads or junk redirects like those “youtube downloader” type sites. Seal is my favorite of the two, but is only on Android.
• Image Toolbox - Insanely feature-packed app for doing practically anything you could want to an image. Converting formats, clearing EXIF data, removing backgrounds, feature-packed editing, OCR, convert to SVG, create color palettes, converting PDFs to images, decode and encode Base64 to and from images, extract frames from gifs, encrypt & decrypt files, make zip files, and a lot more. All local.
• Rustdesk - No-nonsense remote desktop, tons of features, simple file transfer, cross-platform compatibility, and P2P communication without needing a third party server if you so choose.
• LibreOffice - Essentially everything you’d get with Office 365 (e.g. Word, Excel, PowerPoint) but without the $150 price point. Compatible with the same file formats, and has the same functionality.
• Cashew - Feature rich financial app for budgeting, tracking purchases, saving for goals, etc. Doesn’t have automatic import, but I find that manually putting every transaction in keeps me aware of my spending much better than before, so for me it’s quite worth it. Install directly from the APK, or use on web though. The version on the app stores has some features locked behind a paywall.
• Linkwarden - Bookmark manager with cross-platform support, a web interface, automatic tagging, automatic archiving of any saved links in multiple formats, collaborative sharing capabilities, and more. It’s free, but you can also pay $3/mo if you want them to host it for you.

Edit: And Umbrel (on Raspberry Pi) if you want to host things more easily. Basically just a much more hands-off, user-friendly docker for people who don’t want to tinker as much.

Edit 2: Non-FOSS, but Obsidian is the best note taking app I’ve ever used. Great selection of community-made plugins (which are FOSS) for additional functionality, and all notes are in standard cross-software-compatible Markdown. No locked-in proprietary formats.

uBlock Origin leading the pack by at least a furlong.

Godot

I cant believe it has a better user experience than unity, an app that has a 412 USD/month paid plan

Wikipedia. Not an app but still deserves a mention.

Jellyfin.

Wikipedia

firefox

considering the big monopoly of chrome based is not really free, it’s paid by google or microsoft mining user data

SSH.

Alternatively, Postgres.

Fuck apps. Real people use programs.

The Dialer.

• Comes with every phone
• 10+ digit number instantly connects you with millions of people, services, and institutions
• 3 digits connects you with life-saving emergency support
• Very low-latency voice support
• High quality audio (most of the time)
• No ads
• No obnoxious UI

All kidding aside, I’m routinely astounded at how we have yet to top the ease and utility of old-fashioned phone service.

I dislike the implication that the most useful apps are not free.

I always feel more comfortable using FOSS software, even if it doesn’t look as nice as the commercial option.