Personally, it’s impressive you could limit it to just that one. :)
For me, the LZ song that drives the train is ‘What Is and What Should Never Be’. It’s that middle section with the reverb guitar and Plant’s unbelievable vocal.
http://www.youtube.com/watch?v=XtoeOQksSzE
LZ II was one of the first LP's I ever bought. Weird collection, BS&T II, LZ, In-a-Gadda-da-Vida, and Abbey Road.
Something that gets under my skin, a little bit, is the radio practice of playing Heartbreaker, then Livin' Lovin' Maid, then NOT Ramble On! I mean, Ramble On just has to follow Livin' Lovin' Maid.
Out of that old collection, LZ II, BS&T II, and Abbey Road have well withstood the test of time.