E6add9
The most unambiguously cheery and upbeat chord type for the end of a song is the 6add9, or 6/9.
This open-position shape isn’t the most comfortable, but it illustrates the theory… a plain E major with both the 6th (C#) and 9th (F#) added.
E6add9 (type 2)
Don’t confuse the 6/9 with the 13 chord. That would also contain a minor 7th (D), giving rise to bitter self-doubt and tearful blues ballads. This shape is interesting… having the 6th and 9th near the bottom gives an open sound.
E6add9 (type 3)
For most people, this will be the basic go-to 6/9 shape. Omit the low open E and you have a movable shape with the root on the 5th string.
Note how close it is to the familiar old funky E9 shape.
E6add9 (type 4)
Saving the best till last, this is the most beautiful chord in the world. It crops up in no end of different styles.
One day, everyone will end their songs with this chord.