Currently, I'm using Blossom Shower. It's very nice and bright, and it's pink layers make me calm.
I would use Sinnoh Springs if it wasn't missing anything, but I think it still is missing some buttons that all other skins have, so I'll probably wait till it's made perfect.
I'm waiting for a theme to be made after a few months which would be featured around Heart Gold and Soul Silver. I'd like to use such a theme, provided it looks that great as I'm imagining it to be.
Edit: I have just switched to The Plaza. It's good, but I'm not totally satisfied with some of the things in it.