Every piece looks relatively easy before you see the metronome marking.
Schubert. I think this would apply to most of his piano works.
I second that. Especially his last six sonatas, not just because they are difficult, but also because you need to keep up the stamina for close to 40 minutes
I cant third that, somehow schubert is for me typically a composer with no unsuspected technical difficulties :S
try his wanderer fantasy
Anything by John Adams or Steve Reich looks a lot harder than it appears and requires a lot of concentration to play.
Suggestion Diabolique, while not as hard as it sounds, looks fairly manageble on paper, is actually quite tough.
As is the case with almost all Prokofiev.
I'll agree with that. Even the Moments Musicaux, which sound like children's pieces until you try to play them...BTW, Schubert wasn't that great a piano player. He couldn't even play his own Wanderer Fantasy. So why did he feel he had to torture accompanists with the Erlkoenig?
The Earl King is easy--the accompaniment part is, at least. I can understand if you meant this about Liszt's transcription of it, though.
Some may not agree, but I think any pieces by Mozart applicalble to this catergory. Most work by JS Bach too.