Moon River, is a song composed by Henry Mancini with lyrics by Johnny Mercer. It received an Academy Award for Best Original Song for its performance by Audrey Hepburn in the movie Breakfast at Tiffany's (1961). It became the theme song for Andy Williams, who first recorded it in 1961 and performed it at the Academy Awards ceremony in 1962. It also won Mancini the 1962 Grammy Award for Record of the Year and won Mancini and Mercer the Grammy Award for Song of the Year.
Here is an arrangement for Guitar, or Guitar and voice, 3 pages, easy to early intermediate.

"Annie's Song" (also known as "Annie's Song (You Fill Up My Senses)") is a folk rock and country song recorded and written by singer-songwriter John Denver.
Here is an arrangement for Guitar duet, Early Intermediate, with standard notation, guitar Chords, Voice line and Tablature. 
7 pages both Guitars and voice, 5 pages Guitar I, 5 pages Guitar II, Total 17 pages, 2:55' min.
Guitar duet, Acoustic Guitar duet, Guitar and voice. Nylon or steel strings.

Annie Laurie is  a traditional 17th century Scottish song for an unfulfilled love.

For Classical Guitar solo (or acoustic Guitar with nylon strings, fingerstyle).

With tablature. With simple downloadable mp3 just for audio help.

Early intermediate. Pages: 1 page (+1 cover).

When the Saints Go Marching In for Guitar, Bass, Drum trio.

With Guitar tablature.
With downloadable mp3 for audio help.

Advanced Intermediate, 2' min.

Pages: 13 pages. (6 pages full score,  3 pages Guitar with tablature part, 2 pages Guitar in standard notation, 2 pages bass part).

"L-O-V-E" is a song recorded by Nat King Cole, composed by Bert Kaempfert, with lyrics by Milt Gabler.

For acoustic Guitar, intermediate level. With tablature. With melody line. With lyrics.
Pages: 4 pages.