We were originally thinking of breaking through a wall in our bathroom to annex a closet in another room. Because our bathroom is TINY and can use the space. But we finally decided not to, just because we want to keep the house how it is. I admit that up front so you know my bias!
How small is this smallest room? Would it fit a wardrobe? Or even a built-in against-one-full-wall closet?
I've always loved wardrobes. When I was around 12, one of my best friends had a gorgeous old white painted wardrobe. It was shabby chic before that stupid phrase was ever coined. I coveted it so much! It seemed to hold everything cool she owned. She had it decorated much like a locker, so the insides of the doors were covered in photos and stickers. It was just awesome.
And Buffy the Vampire Slayer has a full-wall built in, too. It's awesome.