Love this instrument. I've been playing it since I was... 9 years old I think.
When it comes to classical music, there's no one I respect as much as Beethoven. Learning the Moonlight Sonata was doubtlessly the most satisfying period of the time I spent playing the piano, as it is actually my favorite musical piece of all time.
Though like Fynn, most of my library is soundtracks. My appreciation for piano and soundtracks go hand in hand. One of the earliest piano soundtracks I really fell in love with is To Zanarkand from Final Fantasy X, and it was the first track I taught myself to play all on my own so it'll always have that nostalgic value for me.
I also learned FF IX's Rose of May, though it's been a while since I last played it so I wonder if I can still play it...
Recently as well it's usually the piano tracks that really get to me. Little Busters for example has Parting of the Boys. Umineko has a quite number of them, some melancholic, some hype, and I love them all. On the melancholic side, my favorite is probably this one: