I've been thinking about how to construct bass lines a lot lately. When I'm improvising with a group or when someone brings a song in for us to learn, the 1-5-1 approach almost always fits, and I almost always get positive feedback when I go that route. I know it's "safe" and easy, but there are many expert examples of players doing it with unique voicing that makes it interesting. The one I've been thinking about a lot and annoying my wife with is McCartney's line on "Don't Let Me Down." What's your favorite?