dunst
I use dunst for desktop notifications.
volume.sh and brightness.sh directly depend on the pango features available in dunst, switch from pango_bar to bar for more generic versions...
libnotify-bin
dunst is, for the most part, controlled by notify-send.
rofi
I use rofi as a dmenu substitute
network-manager
Some scripts use nmcli
playerctl
Media players are controlled via playerctl
alsa-utils
Volume is controlled via amixer
maim
Screenshots are taken via maim
fonts-ubuntu
I use the Ubuntu font family a lot...
i3blocks
Allows me to slap together my own i3status replacement (: