"Caroline, No" (1966)
Pet Sounds was such an incredible work of art that many of the songs from the album could have ended up on this list. The amount of sounds involved and the tempo they are set would have gone astray in lesser hands. But again, Wilson's talent for making complex concepts easy for the listener is nearly without peer and could transpose any type of music.
"Caroline, No" is here because of its aching reaction to lost innocence and how Brian Wilson is able to emote this. What other artist could churn out a song that is slow jazzy ballad with a harpsichord that ends with random city sounds and have it all make sense and with beauty? Probably only the collective excellence of Paul McCartney and John Lennon and the singular brilliance of Brian Wilson.
"Sloop John B." (1966)
The origin of this song is from the Bahamas in (likely) the 1800s. After being covered by lots of various artists, the Kingston Trio recorded a version in 1958 and changed the chord arrangement a bit. This directly inspired what the Beach Boys would do with the song. In essence, what was once a provisional tune was turned into a folk melody and the Beach Boys made the track into surf-folk.
Yet another track from Pet Sounds, the track has an irony that oozes. The words are about a boat wreck but the music is tongue-in-cheek. You might have been singing this song in assemblies in elementary school in the 1970s and unaware of the track's meaning. It's a fun song about a situation that is anything but.