ColorZilla is what I use to grab colors to play around with when I'm making skins.
I have FoxyProxy installed but I'm not sure what it's for, don't use it and don't remember adding it.
I have Animated Matrix for my Appearance. It was distracting at first but I forced myself to like it.
I had GreaseMonkey but I uninstalled it because I couldn't figure out how to uninstall this.