Can't think of any nsecbunkers that you can run on desktop, unfortunately. I really want to make one eventually.
Graphical:
Redshift - really strong blue light filter. You can filter all blue light at night at 1500k. Really great.
Clementine - great music player if you have a local library.
Okular - the best pdf viewer
Gimp - image editor
Libreoffice - office suite
KDE connect or LocalSend - I use kde, but considering trying LS to share files across devices
Tailscale - connect devices over direct, secure channels
Obsidian - obv
OBS studio - screen recording and streaming
Deluge - torrent client. I actually run the deluge server on a different machine and only have a client on my PC.
Zint - generate barcodes and qr codes
Variety - wallpaper slideshow
Audacity - audio editor
Kdenlive - video editor
Terminal:
Neovim - you can use any text editor or coding program, and that's fine. But neovim is the best. Sharp learning curve, huge payoff.
Tmux - windows inside a terminal. You can get nvim and tmux to play nicely together. A common theme if terminal life is lots of configuration and headaches, but once it works it works forever.
Ranger - file explorer, vim-like navigation
Chezmoi - many things in Linux are configured in .dotfiles. chezmoi let's you have a git repo that keeps a backup of all of them. Some go a step further and use NixOS, which lets you configure your entire is from specification files.
This list is harder to write because I can't just scroll through all the terminal programs I have installed. You typically just install what you need.