Okay so, Stila and Kat Von D are probably the best two because the pen is really easy to use and the formula lasts. I think KVD is a little better, but you HAVE TO get the tattoo liner and not the ink liner, the ink liner sucks. Also, some people are against KVD because of some of the things she's said and done, so if that's important to you, you may wanna do Stila.
They are I think $20 or so. If you don't want to spend that, I think Nyx makes a pretty good dupe - the Epic Ink Liner, it's like $11 or $13. I really like it, except twice I've had my pen explode on me after a few weeks of use. It hasn't happened to every one, but two of them. Also it happened after I flew with them, so that may be the issue. You can find them at CVS/Ulta/Target.