I always found that silly. Who cares if everyone and their mom likes it? Are you only "cool" if you like pieces that not many people have heard of?
Why do you think the pieces are overplayed to begin with, maybe because they're completely awesome? 
Wow I come back to this thread and see that I'm getting bashed for a light-handed comment.
I have absolutely nothing against liking overplayed pieces. Beethoven's 5th, pretty awesome stuff. Beethoven's 9th is an absolute masterpiece (though that brings up another issue, most people have only heard the Ode to Joy theme and not the rest of 50 minutes of amazing music). The problem is when people decide that Clair de Lune (which hasn't been mentioned in this thread, so I'll use it as an example to avoid offending anyone) is the OMG MOST AMAZING BEAUTIFUL THING EVER DEBUSSY IS AMAZING when they haven't really listened to much else by him.
Just clarifying, I'm not assuming you only listen to the overplayed. You could have listened to other pieces by Debussy (still using the Clair de Lune example) and still decide that Clair de Lune is your favorite. But if Clair de Lune is the ONLY piece you've listened to by Debussy, then it's time to expand your horizons.
And I'm NOT listing pieces no one's ever heard of. And if I did, I don't see how that relates to making myself look cool. It's not trying to be cool or anything. It just is.
I totally agree, Blink83.
I guess you're only cool if you say something provocative and esoteric like, 'the E flat major scale is so beautiful, you will never understand it's beauty (until you've played as many pieces as I have-- please ask me which ones I've played and what level of pianist I am and how many famous performers I've met in person)'.
There's a reason why some pieces are played a lot and some are not. Yes -- Beauty is in the eye of the Beholder -- but there is a reason why there are popular pieces; more people like them than others.
Okay, why do you feel it necessary to be so hostile towards me?
Something provocative and esoteric like "E major scale is so beautiful, you will never understand it's beauty until you've played as many pieces as I have-- please ask me how good I am at the piano and how many famous performers I've met."
Is that supposed to be me? It doesn't take much to hear beautiful music, and to be able to judge what is beautiful. All it takes is an ear. You don't need years and years of experience to listen to music. How the heck am I being esoteric? For your info, I'm not very good at piano and probably can only play about half of the pieces I listed. And I don't believe I've met very many famous performers (I did bump into Joshua Bell once, but that was a coincidence.)
All I said is that a lot of pieces here are overplayed. Not that people who list them should go die or anything..
Why do you even bother listing them? is it because it suggests you have listened to all of their pieces, something we could only dream to do?
Oh so now you decide to pick apart what I say to attack me?
First of all, I listed Haydn because THE THREAD SPECIFICALLY ASKS FOR HAYDN. I just never really felt particularly interested by Haydn's music.
Brahms, I forget why I listed him. adjkjcv;kbjxv I just realized how much great stuff he's written o.o; I guess I just wasn't big on his solo piano pieces.
Mendelssohn. I just don't like much Mendelssohn. It just doesn't move me as much as other romantic composers.
Gershwin. I SAID HE WAS COOL. WHY YOU BASH ME FOR IT??
It suggests I have listened to all of their pieces? How does it suggest that?(Though I have gone on Chopin and Rachmaninoff marathons where I try to listen to their entire ouvre. I never finished for some reason, but I did discover some nice pieces.) Sure I've listened to several pieces by these composers, but most certainly not ALL. Not even MOST.
All in all, WHY SO SARCASTIC??