[DISCUSSION] What are some good songs to play when I'm in a chill or quiet, low kind of mood?

Sometimes I just get in those moods where I want to play guitar for hours on end because of whatever reasons but obviously sometimes I don't want to have a hardcore session of ACDC or Led Zep. I know a few but I was just wondering what everyone's favourite songs were to play or if anyone has any suggestions of songs that are nice to play just to chill?