Oh..this had to be the first post I made on the TCM forums.
Being that I am female, I will answer with my male response first. Clearly my moment, would be on the set of "The Third Man" I turn around, and there is Orson Welles, and he gives me that look. (You know that look, the one he gives Holly when he first sees him) I am done for, a puddle on the floor.
And while we are speaking of breathtakingly beautiful, I cannot leave out the ladies, and cast my vote for Marlene Dietrich and Lauren Bacall.