TWRoO on 01 December 2011
The end of the final episode of Blackadder Goes Forth, a very moving scene that is such a contrast to the rest of the show, and makes you remember when it was actually set. (the series being set in the First World War didn't really focus much on the war)
http://www.youtube.com/watch?v=IglUmgYGxLM
Also, not exactly a specific scene, but my favourite sci-fi episode of all that I have seen is Farscape: Through the Looking Glass from season 1, where Moya gets split into 3 dimensions, one has a red hue and causes some of the crew sickness, one is blue and has an earsplitting background noise and another is yellow and causes hysteria.
http://watchseries.eu/episode/farscape_s1_e17-51379.html
