Possibly The Nicest Song Of All Time

[ER]

Louis Armstrong, What A Wonderful World

https://www.youtube.com/watch?v=A3yCcXgbKrE

[Allhallowsday]

I think it's the performance, the recording, and less the song.  I'm partial to this performance as far as "nice" recordings go: 

http://youtu.be/z_AQMaqDLtg   

[BoyScoutKevin]

Louis Armstrong, What A Wonderful World

https://www.youtube.com/watch?v=A3yCcXgbKrE

I think I'll always remember this song, because this was the song on the soundtrack, when in Finding Dory, Hank the Octopus, drives the truck from the marine park, containing the marine life, off the road and into the water, and everybody, including myself, in the theater, just broke up laughing.