Here are some cool singles-based songs (as opposed to taking every song Zep ever put on an album) that I don't think got picked:
Rock The Boat. It's arguable, but this may be the first "disco" record. Or maybe it was....
When Will I See You Again, Lead singer has just a bit of a lisp

Been in love with her since I first heard this song.
Wildwood Weed. Jim Stafford was a great songwriter and a pretty damned good singer to boot.
Mandy, who gave without taking
We Never Danced To A Love Song. This is probably TMI, but I got laid more playing this record than any other. Plus, I like the subtle dig at everyone having to go disco in the late 70s - Manhattans said "#### that, sometimes, and just hold each other close"
Run Joey Run. If this ain't the pinnacle of 70s drama-songs, then the next one is.......
Wildfire