20. Good Riddance (Time Of Your Life) - Green Day
The History: Hands down, this song is in the top three of Green Day's most popular. The song was released in 1997 on the band's fifth album, Nimrod, peaking at number 11 on the UK Singles Chart and eleven on the Billboard Top 40. Since then, it's been used at every other graduation, and probably will be until the end of time.
Why It's Great: If there's a message to take from this song, it's that not all break ups end up badly with one or even both parties wanting to slash the other's tyres. Sometimes, after some time has passed, we can mend our relationship with this person to have a friendship.
For those people, this is the song for you. The song talks about being at a fork in the road, that it's unpredictable (much like a break up). However, ultimately whatever road we chose was the right one. There are no hard feelings in this song, just a simple but wonderfully compelling message of "I hope you had the time of your life"
To have nothing but good wishes for your ex is something rare, and a song that shows them off is more rare than that.