I dunno, for me its gotta be Zeppelin, anything up to Physical Graffiti. Bonham totally introduced a whole new dynamic to rock drumming, and is one of my biggest influences to date.
And of course, YYZ is unparalleled.
Rush went to my school, by the way (junior high & highschool) I have a copy of Alex Lifeson's shop report card. He didnt do that well. Also, one of my good friends resides 3 houses down from Geddy Lee's old house. Sorry just felt the need to brag concidering this thread had so many rush references.