Which episode of Star Trek: The Next Generation was amongst one of your favorites?

Here: use IMDB to research the name of the episode and if you have multiple favorites, then just post them all. This isn’t a poll here, but if you list more than one episode, all I ask is why you really liked that episode moreso than the rest of them.

http://www.imdb.com/title/tt0092455/episodes

I must have seen each episode at least twice so I have total familiarity with this series so I am wide open to any sort of discussion here.