In the past I've used the Eyeko liner that Alexa Chung always raves about but I found over eye shadow it really dried it out and made it unusable. I've also used ones from various brands in the past such as MUA but found they just weren't as pigmented as they could be so I've used Rimmel's Exaggerate liquid liner a lot in the past although I find it just a little bit watery and harder to control.
Soap & Glory's Supercat liner has the really easy-to-use felt tip which I love that isn't dried out by using it over eye shadow or powders. It's really black and the nib is hard enough that you can get a really thin and defined line which I really love at the very ends of mine, even if I thicken them up in the middle. It is wet enough to get through that and if you wanted you could smudge it out a little on application if you're quick. After that it does set and stays in place all day but it is by no means a waterproof formula and when I tried this on the back of my hand it smudged right off when I washed them the first time. Unless you have really watery eyes or wipe your eyes a lot you'll be okay though and it does stay in place all day.
If you are searching for a new liner or just getting into it then this is a really brilliant one to try. If you're starting out with it then this one gives you the most control and is more like a pencil but it flows more easily across the lid - I wouldn't jump in with gel or liquid when you're practicing!
Let me know what your favourite eyeliner is to do a feline flick with!