Oh, looks like I am in the minority lol - I know it is probably a controversial choice but while the show itself had some troubles I think the Dollhouse theme was great - the plinkety plonkety piano bit at the end is inspired imo.
I have always loved the theme to BtVS. So much so that it was the first and only ring tone I've ever bought,for my mobile phone.
I'm still using the Buffy theme today.