music: mpg123 (with an ncurses frontend I wrote myself)
video: mpv
music/video streamer: pianobar
file manager: vifm
irc client: none (I've never been into chat)
terminal emulator: st
system monitor: htop (but only when something is slowing my system down. Otherwise I don't bother.)
text editor: vim
screenshot: scrot
torrent client: rtorrent
image viewer: sxiv
mail client: mutt
shell: ksh
other/fun: less, vidir, ncdu, par, wyrd, wcalc, elinks, curseradio-improved, rawdog