This is my new favorite cosmetic product hands down. It costs a dollar and works really well. This stuff truly is waterproof--it mostly stays on through a shower (but yes, you still come out looking like a hot mess) if you don't remove it beforehand. This eyeliner comes in a good range of colors, but my local Target only had Black and Coffee:
Coffee on top vs. Black on bottom
Coffee is fairly dark compared to Black, so I guess the color choice is down to personal preference, but when it comes to performance there really isn't a difference. I dying to try ELF's other color eyeliners!