There is a large amount of quality free and open source software (FOSS) available in the Arch and AUR package repositories.
Here is a selection of my favorites. Leave a comment with your own list of favorites and I'll add them to the list!
All of the tools listed below are free 🆓.
Open source tools are marked with a 📝.
File System
🆓📝 Krusader: two-pane commander style file manager.
🆓📝 GParted: disk utility, formatting and partition managager.
🆓📝 balenaEtcher: utility for flashing OS images to USB media.
🆓📝 Meld: file and directory diff and merge tool.
Utilities
🆓📝 CopyQ: pasteboard for storing history of clipboard contents.
🆓📝 Xpad: sticky notes for the desktop.
🆓📝 Albert: keyboard application launcher.
Office & Text
🆓📝 LibreOffice: premiere office suite including word processor, spreadsheets, drawing, presentations and more.
🆓📝 GVim: graphical interface version of vim.
🆓📝 Remarkable: preview markdown files.
🆓📝 Trelby: write a screenplay using standard rules.
🆓📝 Xournal++: note taking software and annotation tool for editing PDF files.
Programming
🆓📝 VS Code: an excellent lightweight open source programming enviroment compatible with a large number of languages and extensions.
🆓📝 GitAhead: graphical interface git client to help you understand and manage your source code history.
🆓📝 Insomnia: a REST client useful for testing APIs
🆓📝 MySQL Workbench: a visual database design tool for administration, database design, creation and maintenace.
Audio
🆓📝 Audacity: easy to use multi-track audio editor.
🆓📝 Ardour: digital audio workstation useful for recording, editing, mixing and mastering audio and MIDI projectsm.
🆓📝 LMMS: a digital audio workstation for creation of melodies and beats, synthesis and mixing of sounds, and arranging of samples.
🆓📝 Mixxx: a full-featured DJ mixing station for mixing music live.
Internet
🆓📝 Chromium: an open-source web browser using the Chromium layout engine that aims to build a safer, faster, and more stable way for all users to experience the web.
🆓📝 Firefox: an open-source web browser using the Gecko layout engine to render web pages, which implements current and anticipated web standards.
🆓📝 FileZilla: a secure SFTP (secure file transfer protocol) client.
Graphics
🆓📝 GIMP: a full-featured image editor and manipulation program.
🆓📝 Flameshot: utility for taking screenshots.
🆓📝 Inkscape: professional quality vector graphics software.
🆓📝 ColorGrab: color picker to detect colors from photos and images and display their color values.