Here's an obscure one:

I played the heck out of Donkey Kong Land back when it first came out - it had its charms, and my options were more limited back then.

So I was quite surprised when I read this in the TVTropes article on "Wasted Song":
King K. Rool's final boss music is only heard in Donkey Kong Land if the player finds every secret area in every level of the game beforehand. Otherwise, the regular boss music plays.
You can hear the theme in question at http://www.youtube.com/watch?v=uWhDbVTsk80 and on http://tcrf.net/Donkey_Kong_Land , where it is stated that it is "unused". I certainly can't recall hearing it before, and the examples of the boss fight that are on Youtube don't seem to feature it.

Is TVTropes wrong in this instance?