Led Zep, just about the best heavy'ish rock band I've ever heard.
As for my favourite track(s) well, I love the immigrant song, Kashmir, Tea for one, most hi (the live version from TGI Friday), you shook me baby, when the levee breaks, black dog, stairway etc.,
I think I like Kashmir the best because of the way the song unfolds, the DADGAD tuning, The drums in 4/4 while the guitar is in 5/8 so it cycles round!
Phill