Oh god, the most difficult thread I've ever had to post on. My Favourite band ever. If you can, get the DVD as the live stuff is fantastic.
I can't pick one, but this lot always float my boat!
Good Times, Bad Times (For the sheer force of nature that was John Bonham and one of Page's great early solos)
Dazed and Confused (Heavy Metal owes a debt to this track)
Whole Lotta Love (ONE RIFF TO RULE THEM ALL!)
The Lemon Song (Showed why they were the greatest white blues band in music. Listen to Hendrix doing Killing Floor which is essentially the same song and Zeppelin stamp on it from a great height)
Since I've been Loving You (Superb Blues Ballad)
Black Dog (Because no other band could have really got away with it!)
Stairway (Because it's Stairway...and the fact that Page improvised the solo in one take after picking up a guitar he hadn't used in nearly three years)
The Rover (My all-time favourite Guitar solo)
Nobody's Fault But Mine (Love the harmonica on this)