Too Faced 3-Way Lash Lining Tool:

This genius little liner takes care of a bunch of eyeliner problems all at the same time: The triple tip allows you to evenly fill in the spaces in between your lashes, which ultimately makes your lashes look thicker. Plus you can use it as a more standard eyeliner–the felt tips come in different sizes for thicker or thinner eyeliner. No excuse for not achieving that perfect winged liner.

Sephora, $22