Songs that never cease to absolutely amaze you

Tool - Eulogy, Prison Sex, Lateralus album, Third Eye, 46 & 2, pushit (salival version is better) , Stinkfist

Opeth - Demon of the Fall, Credence, Karma, April Ethereal, When

Yes - Fragile album (I've only been into them for a little while though)

Phish - You enjoy yourself

ISIS - Oceanic album

Nirvana - Every song kurt ever sings freaks me out because he's dead and I can't believe it... still.

Emperor - Anything from 9 EQ, Nightside or anthems especially.

Death - Every tune these guys (chuck actually) wrote .. I miss you chuck R.I.P
 
I doubt that anyone seriously reads every reply here, but here are a few of my faves anyway. :)

Amorphis - Black Winter Day
In Flames - Moonshield, Only for the Weak
Opeth - The Moor, Harvest, Credence
Lacrimas Profundere - Diotima
MDB - The Cry of Mankind
Whispering Forest - Flamescape
After Forever - Leaden Legacy
Nightwish - Crimson Tide
Tristania - Most of the Beyond the Veil album
A Perfect Circle - Judith
Tool - Schism, Lateralis, Forty-Six & 2
NIN - Just Like You Imagined and a ton of others
Paradise Lost - One Second, Ordinary Days
Blind Guardian - Harvest of Sorrow, Thorn
Ayreon - Dawn of a Million Souls
SymphonyX - Communion and the Oracle
Therion - Asgard

Damn, that's much longer than I expected. Hope that answers the original question. :)
 
Pantera - Cemetary Gates, 25 Years
Social Distortion - I Was Wrong, Ball and Chain, Down Here With the Rest of Us
Emperor - Curse You All Men, Inno A Satana, Thus Spake the Nightspirit, With Strength I Burn
Nevermore - Dreaming Neon Black
Soilwork - Chainheart Machine, Bullet Ride
Virgin Black - Muesum of Isacariot
Pink Floyd - Shine On You Crazy Diamond
Buckethead - anything from Colma, Destroyer
Steve Vai - Kill the Guy With the Ball, Bad Horsie, Giant Balls of Gold
Joe Satriani - Motorcycle Ride, Flying In A Blue Dream
The Gathering - Strange Machines
Tool - all of Laterulus (lately)
Metallica - Blackend, Orion, Sanatarium
Megadeth - Tornado of Souls, Peace Sells, Sweating Bullets
Agalloch - In the Shadow of Our Pale Companion
Blind Guardian - Nightfall In Middle Earth
Porcupine Tree - 4 Chords, Blackest Eyes, Lightbulb Sun, Sound Of Music
Opeth - The Drapery Falls, Funeral Portrait, By the Pain I see In Others, Demon of the Fall