A couple of my favourites:
Chopin: Op. 64 no. 1 - 'The Minute Waltz': A long time favourite of mine, I always wished to learn it on the piano for the fun of it. Not a favourite favourite but one i'd be happy to listen to if it came on the radio, etc.
Pathetique pt. II: Sorry, this could actually be called 2nd movement, i'm not entirely sure (I looked in Teran's pathetique for this part of it but couldn't find). Anyway, this is beautiful. It weeps emotion and if i'm not mistaken, a version of this was played on Crystal (or Krystal) night. It was the night that signified the end for many Jews in Western Europe in the Holocaust. The Orchestra playing it were Jewish and knew that they couldn't get out of the country in time, thus they still played the piece that night, knowing it was likely their last time playing music in an Orchestra. The version they composed has very few records but my family does have one of them and while I haven't listened to the exact piece i've been told that it's one of the best versions ever done.
Basically this piece carries with it a lot of meaning for me.
Moonlight Sonata: A piece that I learnt a lot of on the piano by ear. Again, a beautiful piece that I find invokes images in my head, often the classic lake turned silver by the moon but sometimes other images.
On to other types of music:
Mumford & Sons: Little Lion Man: An incredible song that makes me think of the wild savannah every time (don't kill me for saying that just because of the title - the rhythm of the song and the way it's depicted also contribute to that!).
Jason Mraz: Lucky: A great duet. I don't know what else to say about it.
Trivium: The end of everything (+ Rain): The end of everything is stunning. Done by a metal band, it leads in to Rain which is by all standards a full on metal tune but the two do fit together. The end of everything is a truly amazing piano piece which, added to the increasingly climactic choir voices with it just make this beautiful piece. Can't recommend it highly enough. As a special mention, a similar piece which I enjoy, which is like this piece is
No dreams breed in breathless sleep by dissection which is also melodic and beautiful in a darker sense. It's also something that you'd expect to hear in Game of Thrones, which is kind of cool haha.
To OSTs:
Final Fantasy V: Dear Friends: This piece is particularly suited for remembering old times and past friendships, in fact it entirely suits an online game I play known as Oberin for it's unique-ness and incredible community (I mean, Smash has a fine community but honestly, i've never met such an incredible group of people playing Oberin. It's lifespan probably isn't very long now because Lion can't support it and the way around that has peroblems associated with it. However, it will always be a game i remember and treasure). It's original version is the best and it's a rather beautiful tune to listen to. In the game itself, it is played after the final battle when [I think it's] the protagonist (or possibly a secondary character) reflects on what happened to the four characters in the years following the final battle.
Chrono Trigger: Boss battle 2 (The battle at hand!): I was thinking of putting up another FF piece but come to think of it, a lot of Chrono Trigger's tracks are really, really good. It's a piece used when you fight a significant and important boss and they're usually extremely difficult (gah mr. T-rex!). The music suits the epicness of the battle and is really fun to listen to when fighting them.
My final two come from the same game, one is longastanding, the other new. These are my top two:
Terranigma: Sadness (remastered by kitara): The actual piece from the game was okay, not one of my favourites but decent from the awe-inspiring soundtrack from this game. This remastered version of it rockets it up to number two though. It's taken up to the next level and puts a ton of emotion in to it that is magnified if you've played the game (which is my favourite game of all time). Really beautiful and also rather sad, though inspiring and almost happy at the same time. it's hard to capture the true feel of the song. It's worth listening, though.
And my final, all time favourite is:
Terranigma: A hero's final day: It may seem fitting that my favourite song comes from my favourite game. This piece is fraught with emotion and it made me cry at the end of Terranigma, one of the few games that has left me crying by the end. However, it's also the beginning of something new.
I can't say more about this piece without becoming emotional haha. Playing the game is my preferred method of being introduced to this piece but if you're not going to play the game then listening to it this way is fine. ^^
So there's a top ten for you. I hope you enjoy!