If there is one Lisp function/macro/feature that you would like to see in a non-Lisp language, which one would it be?

This is another Friday social topic. You are aimlessly wandering around a beautiful hilltop by a sea when an angel approaches you from the opposite direction. She is no ordinary angel. She is a Lisp angel! She will grant one Lisp wish to you. Before she can fulfill your wish, she needs this information from you:...