My all time favorite is probably in For the Love of God by Ulver, but other amazing ones are:
Genocide-Judas Priest
Slayer-Evil Has No Boundaries
Kreator-Total Death
Yeh evil has not boundaries is pretty sick solo, most stuff on reign in blood is really good. Also, a lot of solos from early Mercyful Fate songs, like nuns have no fun, melissa and such are really cool. I have always liked the 'one' solo by metallica and fight fire with fire.
Inpropagation - carcass
The principal of evil made flesh - CoF (i like it, so what)
Kreator - impossible brutality
are just a few i can think of from the top of my head
Arch Enemy - Burning Angel
Behemoth - Conquer All
Carcass - Buried Dreams
System of a Down - Streamline
Led Zeppelin - Stairway to Heaven
At The Gates - Cold
Vader - This is the War
Metallica - Ride the Lightning
Judas Priest - Painkiller
too many good solos out there...but right now I'm thinkin Evergrey - Trilogy of the damned...it's pretty basic but extremely effective. you really feel the notes...
A lot of old 70's Classic Rock stuff does it for me, but other than that.
Arghoslent - Heirs to Pedition
Arghoslent - Of Spears and Horns
Arghoslent - The Negress
Slough Feg - Sky Chariots
Behemoth - Conquer All
In Flames - December Flower
Blood Red Throne - Bleeders Lament
Infernal War - Crushing Impure Idolatry
Intestine Baalism - The Planet
Yngwie J. Malmsteen- Black Star, Far Beyond the Sun, Evil Eye, Icarus' Dream Suite Op. 4, Little Savage, Disciples of Hell, Trilogy Suite Op. 5, Heaven Tonight, Krakatau, Blitzkrieg, etc.
Marty Friedman - Lucretia
Jason Becker - Mable's Fatal Fable
Tony MacAlpine - Christmas Island
Michael Romeo - Accolade II
Al Di Meola - The Romantic Warrior, Fantasia Suite
Steve Vai - For the Love of God, Crying Machine
Joe Satriani - Friends
Megadeth - the intro to 'Good Mourning/Black Friday'. It builds up very well.
Metallica - 'Shortest Straw' and 'One' ...or whichever one I happen to be learning at the moment, which is 'Eye of the Beholder'.
Slayer - all of the solos from 'Altar of Sacrifice/Jesus Saves'. I like the way Hanneman and King play off each other in these songs. It reminds me of watching Tom and Jerry in the way that King and Hanneman seem to chase each other with their solos sometimes.
RR United - 'In the Fire' (the best song on that whole CD, in my opinion!). I was actually surprised by that solo - the boys from Trivium did a decent job with the solo. It might not be on anyone elses list, but I liked it.
...that's all off the top of my head. If I really put some thought into it, there would be some Randy Rhoads, Hendrix, Van Halen, Azagthoth, James Murphy, etc. etc. What an awesome thread...