And you may have thought it tragic
    Not to mention other adjec-
    -tives...

is also pretty great. Then there's the absurd chain if "-ility" rhymes in When You Are Old And Gray.

I would say his "elements" song holds that spot:

    These are the only ones of which the news has come to Harvard,
    And there may be many others, but they haven't been discovered.

My favorite rhyme comes from Perry Como:

The way that we cheered/whenever our team/was scoring a touchdown,

The time that the floor/fell out of my car/when I put the clutch down