i'd have to think long and hard on some of the categories but right off the top of my head my vote for four (you mentioned misc. so i'll use that for transcriptions though i think they should be their own category)
fugue-Taneyev- Fugue in g# minor from Prelude and Fugue in g# minor Op 29
wickedly hard:
Etude-Gyorgy Ligeti's 'Devil's Staircase (L'escalier du diable) (famous for the Shepards scale and the dynamic marking 'ffffffff'
transcription-Igor Stravinsky's Firebird Suite (Danse Infernale, Berceuse, Finale) arranged by Guido Agosti(this is my favorite video of it)
concerto (i'll use this for a piano plus orchestra work not neccessarily a concerto/sonata form)
Strauss Burlesque d minor for piano and orchestra (i think this was called unplayable for a little while)