Registry Shield, great idea, got my vote, could it be light on resources too?
There are a number of tools out there that can do the job (Diamond CS's RegProt, etc.) but people have to know about these and be able to find them.
I think because they only intercept registry changes (and most spyware/malware need to create a registry entry) and ask permission, resources shouldn't be high. So could this give avast another string to its bow, further protecting the user without becoming a resource hog?