I have to go with some already mentioned:
Gilmour "Comfortably Numb"
Cedrone "Rock around the clock" (Talk about avant-garde shredding!!!)
Scholz "Gonna hitch a ride" (for the Boston-fans, especially check the part (re: short burst) that starts at 3m20sec.. ROCK!!!!
Clapton "Crossroads"
EVH "Eruption"
but I'll add some:
whoever in Mercyful Fate played the intro solo of "Corpse without a soul" FREAKIN' AWESOME!!!!! Metallica wussed out and skipped it on their cover version on Garage Days.
Richie Blackmore "Mistreated" (Yngwie's version is even heavier, but too much meedley-meedley-wiedley-sweepie....)
Slash "Perfect Crime" That fast part makes my adrenalin go nuts!
Angus Young "You shook me all night long" nice and basic.
Ace Frehley "Shock me" I was assigned to do that solo note by note at a guitar-tentam... I rocked and conquered...
Al DiMeola "Egyptian Danza" tried to figure it out and let it be after 20some bars... too damn hard!
Judas Priest (dunno which of the guitarists) "Dreamer Deceiver"
Kevin Heybourne (Angelwitch) "Freemen". I want this song to be played on my funeral! Dead serious! (no pun intended)
Whatever "Comfortably Numb's" solo is to classic rock, is "Freemen's" solo to hard rock/heavy metal.
Edit::
add these too:
Dan Spitz (Anthrax) "Panic" cool twin solo also...
Marty Friedman "Holy wars"
Randy Rhoads "Mister Crowley"
Dave Murray (Iron Maiden) "Strange World" (both soli)
Judas Priest "Hell bent for leather"
Judas Priest - all those sick sweeps from "Painkiller" are pretty awesome...