I'm also going to chime in on guitar riffs being more memorable than first lines. Whenever I hear the Edge's repetitive guitar, it sounds like a train, headed somewhere in a hurry and you don't want to miss the ride because it's going to be incredible. That much said, if I had to pick one song line, it would be "you're dangerous, cause you're honest". I wish I had valued that advice more when I was in my 20's because now in my 50's I can see past my ego and understand that honest people, whether you are on the same or opposite sides, offer respect regardless of your feelings. Be it in business, relationships or whatever.
Our friends love us and the ones willing to call you on any bullshit is solid. Same goes for your foes.