XSS isn't only about SCRIPT tags. What about javascript URIs, IMG and IFRAME tags, flash elements that you can add in a page by XSS? Filtering what is shown to the user is still the best solution IMHO.
Do you mean filtering what is sent to the browser - validating libraries so user input cannot generate URIs, IMGs, etc?
<iframe src="data:text/html;base64,PHNjcmlwdD5hbGVydCgnRk9PQkFSJyk8L3NjcmlwdD4="></iframe>