Make the Web Nice and Dark (and still work) - updated Stylish styles
Firefox and Chrome) and like dark global themes, you might want to check out my global dark web theme. It's a fork (meaning I'm starting with someone else's template), but I'm slowly making it my own and keeping it updated. And this is also the style I use on a regular basis, so things that are irritating are gonna get fixed.
Darker Remember The Milk. I also use Remember The Milk for my chores and stuff on a daily basis, so this gets updated when things break.