OK, OK, so this is an easy one to recommend. But if I have to choose a favorite Zep album, I think it'd be this one (or would it be "Presence"...?). A while ago, I sat down with this record and the Led Zeppelin Complete songbook and tried to learn every part of every tune. I think even just The Lemon Song could keep you occupied for a while, with its main riff, the fast chordal parts, the slow bluesy solo, even John Paul Jones' oh-so-funky walking blues lines underneath Jimmy's solo. Jimmy's solo break in Heartbreaker still holds up well over time, and contains many of the classic elements of his incredible style. One other thing of note: this is great stereo album. Listen to it through headphones to get the full effect - especially the middle section of Whole Lotta Love, and the end part of Ramble On.