It is important to note that I have never been very much of a eye liner snob. When I first got into makeup I always created my own liners that were eyeshadow powder based. I felt that the powder colors I already owned gave me the most versatility and options for use. I could match the colors perfectly to whatever I was doing and was able to make my lines look as blended or precise as needed. The more adventurous and more creative I got, the more I ventured into buying actual kohl liners. Initially I kept to a drugstore brand grey that served as a foundation for my powders and wasn't visible when covered. I began to branch out when I needed something to make my looks more intense or severe. My adventurous tendencies have allowed me to make the following two recommendations.
Steal: Sephora 12 Hour Wear Eyeliner
This purchase was a total impulse buy. I happened to be browsing a Sephora when some neon liners caught my eye. After testing them on my hand and loving their potency and vibrance I was sold. It took the better part of a day to finally get the colors to come off my hand, which I felt was a true testament to their staying power.
This line offers a massive run of colors (35 total) that allow me to experiment on the inexpensive end. The colors glide on with minimal effort and stay put for the 12 hours they purport, and for only $9 a pop.
Swank: Urban Decay 24/7 Glide-On Pencil
Urban Decay 24/7 eyeliners come in 40 different colors and their title does everything it claims. This eyeliner has the single smoothest application I have ever experienced. The colors are incredibly vibrant and true to every swatch and color label they use. While I most definitely consider these liners a must have, their $19 price tag has me pumping the brakes on impulse buying.
You can buy the eyeliners here and here.