There are few more epic rambling songs than Stairway to Heaven, it provides a pretty astute summary of Led Zeppelin and as an introduction to the band would tell you most of what you need to know, although it lacks the powerful chunky riffs you may find in other tunes. Putting so much great guitar work into one track is well worth a listen, a great bit of acoustic pickiness and a great solo - I was going to say squeezed into a track, but at 8 minutes long there wasn't much squeezing going on here.
I chose this as my performance piece for GCSE music but given that I spent most of my time messing around in the practice rooms doing very little actual practice it wasn't my finest piece, I think at one point I lost time with the backing track and I never quite managed to nail the solo, the switching from acoustic to electric proved to be ambitious as well. Still to this day though over 10 years later I can pick up a guitar and play out the first few minutes of acoustic goodness with no problem - it's engrained in my memory. Obviously I wouldn't try that in a music store of course - "Stairway DENIED!"