A favorite brand of mascara? A hard-to-find shampoo?
I can usually make do without most other makeup, but I pretty much always carry a black Estee Lauder Doublewear Stay In Place Eye Pencil. I know lots of people are devoted to liquid liner, but I guess you could say I'm a traditionalist. That said, I always lose my eye pencil sharpener.
So, what's that one thing that's always in your bathroom? Add it below, would you?