Is there a TV show episode which came completely out of left field and blew you away with how good it was?

About a year ago I was binging through Deep Space Nine, and there was this one episode in Season 4 (Episode 2, The Visitor) which came completely out of nowhere as a mostly stand-alone episode in the middle of a developing season plot. The themes, direction, plot, everything just seemed to come together by chance to create an episode that still holds up extremely well today.

I was wondering if there were any other episodes from other TV's shows where it's a sea of averages/good, but has that one episode which is unlike any other for the entire series that stands out.