Lots of barrettes.
Teeny, tiny barrettes that always get lost.
We don't have much wall or door space in C's room, and don't have room for a hanging barrette organizer (like this, this, or this one similar to what I had as a child). Instead, we just have a little barrette box that sits on a shelf, next to a little bucket of hair elastics.
She has so many barrettes that it's a pain to search for a matching pair. I don't know why it didn't occur to me sooner, but now I've clipped all of the matching barrettes to each other, so that they're in the box in pairs. No more searching! Plus, I've removed all of the singles, and plan to make some felt barrette covers.
Voila! Simple and easy, but it saves me time searching for a matching pair! Now, if only I can get Hubby to clip them together before putting them back in the box...