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 πŸ†“.
Open source tools are marked with a πŸ“.

File System

πŸ†“πŸ“ Krusader: two-pane commander style file manager.
πŸ†“πŸ“ GParted: disk utility, formatting and partition managager.
πŸ†“πŸ“ balenaEtcher: utility for flashing OS images to USB media.
πŸ†“πŸ“ Meld: file and directory diff and merge tool.

Utilities

πŸ†“πŸ“ CopyQ: pasteboard for storing history of clipboard contents.
πŸ†“πŸ“ Xpad: sticky notes for the desktop.
πŸ†“πŸ“ Albert: keyboard application launcher.

Office & Text

πŸ†“πŸ“ LibreOffice: premiere office suite including word processor, spreadsheets, drawing, presentations and more.
πŸ†“πŸ“ GVim: graphical interface version of vim.
πŸ†“πŸ“ Remarkable: preview markdown files.
πŸ†“πŸ“ Trelby: write a screenplay using standard rules.
πŸ†“πŸ“ Xournal++: note taking software and annotation tool for editing PDF files.

Programming

πŸ†“πŸ“ VS Code: an excellent lightweight open source programming enviroment compatible with a large number of languages and extensions.
πŸ†“πŸ“ GitAhead: graphical interface git client to help you understand and manage your source code history.
πŸ†“πŸ“ Insomnia: a REST client useful for testing APIs
πŸ†“πŸ“ MySQL Workbench: a visual database design tool for administration, database design, creation and maintenace.

Audio

πŸ†“πŸ“ Audacity: easy to use multi-track audio editor.
πŸ†“πŸ“ Ardour: digital audio workstation useful for recording, editing, mixing and mastering audio and MIDI projectsm.
πŸ†“πŸ“ LMMS: a digital audio workstation for creation of melodies and beats, synthesis and mixing of sounds, and arranging of samples.
πŸ†“πŸ“ Mixxx: a full-featured DJ mixing station for mixing music live.

Internet

πŸ†“πŸ“ 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.
πŸ†“πŸ“ Firefox: an open-source web browser using the Gecko layout engine to render web pages, which implements current and anticipated web standards.
πŸ†“πŸ“ FileZilla: a secure SFTP (secure file transfer protocol) client.

Graphics

πŸ†“πŸ“ GIMP: a full-featured image editor and manipulation program.
πŸ†“πŸ“ Flameshot: utility for taking screenshots.
πŸ†“πŸ“ Inkscape: professional quality vector graphics software.
πŸ†“πŸ“ ColorGrab: color picker to detect colors from photos and images and display their color values.