I recommend the Urban Decay 24/7 Glide-On Eye Pencil Liner.

Since I have monolids, I pay a lot of attention to my eyeliner. Out of all the products I've tried, Urban Decay's Glide-On is the absolute best, so I'm buying it in every shade. First of all, it doesn't smudge, and since all the shades contain shimmer, even a light line looks a bit glamorous. The shade in the photo is a brown-toned whiskey, but the purple, blue, and green ones are also pretty and not too flashy! Highly, highly recommend it!