The first thing that comes to mind is John Fahey's Sligo River Blues. Simple, but diamond-like perfection, irreducable...

Morrissey - November spawned a monster
Morrissey & Siouxsie - Interlude

The Beach Boys - Surf's up

perfect songs... um.

Unwound "Look A Ghost" is one of many perfect songs by that band. "Terminus" also.
Fugazi Life & Limb
JOMF- Your cells are in motion
Drive Like Jehu- Do You Compute?, bunch of SY songs, couple Nirvana songs, and more songs than I can write down or care to.

Color Me Badd by Land of Talk

FUCK YEAH

Nefeli is on a roll! you've picked some good choices there, especially Herb Diamante, The Orb and Babes songs.

perfect songs
 

Youve got it right. Perfect-Perfect runner-runner meaning there are 2 and only 2 cards and you need both is a 989-to-1 draw. I believe thats what your calculation would come out to if you inverted the decimal.

ive been obsessed with this morricone piece recently. the movie is also pretty good
http://www.youtube.com/watch?v=YsfBSs5bDbE

Quick Canal by Atlas Sound.

Instrumental but whatever:
John Coltrane - After the rain

Roy Montgomery - 2LB
http://www.youtube.com/watch?v=nzzPJk3aBjc

I think it was this piece

http://www.youtube.com/watch?v=BH5jmi0A-aw

Incredible!

yeah, that is what i had posted!
and murmer, that is an amazing fahey piece.

Laura Palmer's Theme - Angelo Badalamenti

queued to my favorite part...

http://youtu.be/khMlcTE7lw8?t=1m28s

Brainiac - Vincent come on down

mott the hoople-thunderbuck ram

This has got me thinking of all the different ways in which a song can be perfect. I see a lot of votes for lengthy, epic, cinematic songs (A Day in the Life, various Pink Floyd, etc) so that seems to be a predictor of "probability of perfection." Also, songs that seen or feel definitive in some way, which explains the Smiths and Joy Division (and "Good Morning Captain," "Marquee Moon," etc.) and then there are the oddball entries like Braniac, Pavement, Boris, etc. which all seem to represent more of the individual, while those landmark songs often feel like they represent the individual's idea of what s/he might think is an "appropriate" or expected answer.

I really enjoy reading these replies straight through, without stopping to glance over at who said what. This is kind of like porn for me.
But are we answering subjectively or objectively? Speaking just for ourselves, based on our life experiences, or are we providing answers that we feel will be shared/agreed with/common? Either type of "perfect" would be able to carry a thread by itself. The "objective" perfect tells you about culture (e.g., "A Day in the Life," which is probably the first thing that pops into the heads of an entire generation when asked this question. But the subjective kind of perfect is where the real story is.

For instance, why in the hell would anyone call the Cure's "Plainsong" perfect? It's essentially nothing more than a lead in... an intro... To an album that is so full of notoriously "perfect" ( type O) songs that "Plainsong" might as well not even be on the album as far as the legacy of Disintegration is concerned. I mean, who calls "Providence" a perfect song? Or "revolution #9"?

Well, I do. "Plainsong" is perfect. More so than any other Cure song. And without it, Disintegration would lose about 30% of its eerie atmospheric beauty. So why the hell is that song so powerful to me, when most people probably skip over it?

That's what I like about this thread.

Well put, but I would like to think that the stories behind why people choose the songs they choose actually are unique, even if the reasoning behind the decision to place the label, and the song itself, are not.

Using Sonic Youth's music as an example: i don't think anyone would look or think twice at someone calling "Teenage Riot," "Expressway to yr "skull" or "Diamond Sea" perfect (though I'm sure there are still plenty of interesting and unique stories behind these choices). But what if someone chose "Winner's Blues" or "Junkie's Promise" or "Society is a Hole?" What about "No Queen Blues," "Or," or "Heather angel?" Great fucking songs, all. But definitely less obvious and less universal choices. There have got to be some interesting stories behind these picks.

(Btw, I happen to think all of those songs are perfect, and I've certainly got my reasons... Not that they're interesting, necessarily, but I'm sure you get the idea: It's the meaning the songs hold for the person, which is likely based on experiences that are unique, even if they're not earth shatteringly exciting.)

Dark Day - Nudes in the Forest
http://www.youtube.com/watch?v=KDBvynPmcNYthe

I have chosen this song because it's perfect.