I'm a makeup artist at MAC, and I know for sure we have one type of liner that was specifically formulated to be able to use on the waterline, which is the Technakohl liner. The Technakohl pencil is a self-sharpening pencil liner. (
http://www.maccosmetics.com/template...D10346)Anyway, many of the artists also like to use Fluidline, which you can also find in the eyes section on the MAC website, but that isn't what it was specially made to do. Many of the artists like to use it that way because they think it stays better, but I have had great results with the Technakohl. I have hyper sensitive eyes and the Fluidline just agitated them.
Good luck!