Best hard rock song intros of all time? Oy! very hard to narrow this down to a short list as there are so many great intros. Some are great intros on otherwise average songs. Well, I'll give it a shot:
Motley Crue - Kickstart My Heart
AC/DC - For Those About to Rock
AC/DC - Hells Bells
Black Sabbath - Sabbath Bloody Sabbath
Black Sabbath - Paranoid
Disturbed - Down with the Sickness
Judas Priest - The Sentinel
Judas Priest - You've Got Another Thing Comin'
Led Zeppelin - Heartbreaker
Led Zeppelin - Whole Lotta Love
Deep Purple - Smoke on the Water
Deep Purple - Highway Star
Deep Purple - Lazy
Deep Purple - Space Truckin'
Jimi Hendrix - Foxey Lady
Jimi Hendrix - Purple Haze
GnR - Welcome to the Jungle
Derek and the Dominos - Layla
Van Halen - Hot For Teacher
Metallica - Ride the Lightning
Metallica - For Whom the Bell Tolls
Metallica - Seek and Destroy
Metallica - Master of Puppets
Metallica - Harvester of Sorrow
Ozzy - Crazy Train
Ozzy - Rock and Roll Rebel
Pink Floyd - Time
Gimme Shelter - Rolling Stones
That's just off of the top of my head without thinking about it, there's sooo many great song intros.