We have pieces in the following keys for Guitar:
1-20 of 227 Guitar Pieces in C major

Trad.
London Bridge is Falling Down

W C Handy
The Memphis Blues

Trad.
Jingle Bells

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Mary Had A Little Lamb

Gounod
L'Angelus

Trad.
Dixie

Brahms
Finale from Symphony No. 1 (Theme)

Trad.
O Sanctissima (Sicilian Song)

Metallica
Nothing Else Matters

Dowland
Come again

Trad.
In The Sweet By and By

Ed Sheeran
I see Fire

Beethoven
Turkish March From The Ruins of Athens, Op. 1...

Trad.
Hush Little Baby

Trad.
I Love The Mountains

Ivanovici
Anniversary Song (Waves of the Danube)

Tarrega
Malaguena
(subscription)

Reinecke
Christmas Hymn Op. 206, Vol. III

Trad.
Do Lord (American Spiritual)

Beethoven
Romance In F Op.50