What I've wanted for some time, and it seems hard for me to find, is a good ad blocker that only works on blacklists. I don't mind ads on some sites as long as they're non-intrusive. Once they start getting in the way of the content though, I want to blacklist the site. Everything I've seen so far (although I haven't put a LOT of time into searching) only works on all sites by default and you have to whitelist the ones you want to have ads enabled on.