Niccolo Paganini, Romance in A Minor from Grand Sonata for Guitar and Violin!
I'm just practising this piece in a wonderful version for solo guitar, edited by Karl Scheit.
It's an ABA'-form (Piú tosto largo. Amorosamente), very nice and romantic chords, beautiful melodies, arpeggios, scales and octaves.
My teacher said, when he gave me the piece: "Technically not too difficult, but challenging to play it really beautiful"....