More options --
Liszt's transcription of Beethoven 9 is a two-piano arrangement.
Chopin wrote a Rondo for 2 pianos, Op. 73, in C major, that's not performed often. I like it, though it's kind of dry.
There is Debussy's "En Blanc et Noir" for 2 pianos.
Poulenc wrote a Sonata for 2 pianos.
Mozart's D major 2 piano Sonata in KV 448, it's my favorite.
Brahms transcribed his Quintet in F minor, Op. 34, to a two-piano arrangement (Op. 34b). I own it but I have not had a chance to listen to it.