For a piece of FLOSS (free/libre and open source software) to be here, it has to both be personally useful and I have to like it a-lot:

desktop: dwm

web browser: Firefox

development: Emacs, Meld

file manager: Emacs (Dired mode)

misc utilities: ripgrep, Sudo, Lsof, less, procps (top, watch), Ex Falso, gnumeric, coreutils (head, tail), LinkChecker, Iotop, rdiff-backup, OpenSSH, vnstat, tmux, File Roller, youtube-dl