Hate to mention it, but Amazing Grace only has six! And it's 'pentatonic' - you can play it on just the black notes of a piano.

Similarly, 'Morning' from Grieg's 'Peer Gynt' suite (first section before the key change), and that only has five notes... it goes

D B A G A B

D B A G A B

D B D E B E

D B A G

Not forgetting Beethoven's Ode to Joy! But that isn't pentatonic.

See! You can be highbrow and simple at the same time!