I believe that pieces that sound hard and are not that difficult are:
Rondo Op.11 by Hummel, Etude Op. 25 no.1 by Chopin, Gigue from Partita no. 2, Prelude and fuge No. 2 (Bach), Clair de Lune, Chopin's first Waltz, Gypsy Rondo by Haydn... There are many... The Rondo is not difficult, I am working on it. A piece that sounds easy, and it is harder than it sounds, humm... I would say that Brahms' Capriccio Op. 76 No. 2 fit in well... Chopin's Waltz in D flat (Petit Chien).
Mario Barbosa