music: mpd + ncmpcpp
video: mpv
music/video streamer: mpv + youtube-dl (And now mpsyt after reading this thread (thanks guys))
file manager: coreutils + ranger
irc client: irssi
terminal emulator: urxvt + zsh
system monitor: htop + atop + ps
text editor: emacs
screenshot: scrot
torrent client: aria2c (used my own implementation but now using dad + diana)
image viewer: sxiv
mail client: mutt
other/fun: Unnethack
organisation: Org-mode in emacs

Edit - Added mpsyt