Though it isn't quite metal, my favorite solo of all time has to be the solo from the live BBC Sessions version of Thank You by Led Zeppelin. Page absolutely slays on that, oozing tone and emotion.
Second place goes to a definitively Metal solo for the ages, Sails of Charon by The Scorpions. Uli Jon Roth laid down the gauntlet with that track. A total masterpiece.
Then Arcturus' Fall of Man. Carl August Tidemann is the kind of guitarist that makes me weep when considering my own skills. Not just because of his technical ability to play circles around me, but for the tone, the depth of his sound and his control over the emotive possibilities of a fretboard. This solo is, for me, a perfect creation.
As has been mentioned before, Cacophony's Speed Metal Symphony is definitely one of the most ridiculously awesome exhibitions in guitar history. Becker and Friedman together were a force no '80s shredder could touch. I'm also partial to Randy Rhoads, despite not being much of an Ozzy fan. The solos on Mr. Crowley, Over the Mountain, and Mother Earth are legendary.
Carcass' Carneous Cacoffiny is also a favorite of mine, as well as No Love Lost. Carcass solos pretty easily rank above most others in the genre.
The whole of Dark Tranquility's The Gallery is full of outstanding lead guitar work as well.
Vogg of Decapitated is consisent (or was) with pulling off excellent solos. Even though the album itself was a dissapointment, I enjoyed the solos on The Negation a lot.
And how can I go without mentioning Megadeth. Tornado of Souls has long been one of my favorite solos.
And Death! The Philosopher is classic, like so much else of the band's lead work.
Windir's Arntor features some excellently emotive and passionate solo work that rips right through me.
And the brief but awesome solo at 12 minutes into Sacrilegium by Devil Doll.
And I'll stop now...
