Bobbi Brown's Long-Wear Gel Eyeliner.
love this badboy.
I've had it for two years and I have used it pretty consistently since. Consistently in my world is a few times a week, I wear it to work as often as I can (4 days a week I'd say).
As you can see, it's a proper black black. My lids are dark but this comes up a proper black so I'm more than happy with it.
It goes on with ease, is nice and smooth, very pigmented and lasts all day without the need for a primer. You need the tiniest bit and it smudges out very nicely too.
In short..buy it!