I posted a couple of weeks ago about my NYX eye pencil hauls and this is a swatch of all the colors that I have. My most used color is Electric Blue & Sapphire simply because the colors are exptremely vibrant. I love using the Sapphire pencil on my lashline and waterline especially when I'm wearing lavender or pink eye shadows as it makes my eyes pop (!). This goes the same with Electric Blue - I usually use this color on my waterline whenever I use MAC's Blue Peep fluidline on my lashline, I just love the effect it gives to my eyes.
I think the lighter colors such as Baby Blue, Yellow & Baby Pink is an easy pass because they are a little too light (at least for me) to use as an eyeliner. I love it when eyeliners/pencils does its job to enhance the eyeshadow color and the shape of the eye.
And of course, nothing can beat the price tag of $1.99 each eye pencil :)