In December, Google graduated one of the most popular labs, Quote Selected Text, to a full-fledged feature. Due to some confusion, it was quickly moved back into Gmail Labs, where it can still be found.
This is one of our favorite Labs that we wish would remain a permanent Gmail feature.
Quote Selected Text allows users to highlight a portion of an email and click Reply so that only the selected text will appear in the response. By doing so, you can draw attention to specific portions of an email. This is especially useful when responding to a long email, where the response may be confusing without the proper context.