9. FX - Black Sabbath
The whole allure behind Black Sabbath in the early days was just how unpredictable they were from one album to the next. Since the genre of metal was just getting born, fans were more than happy to go along for the ride with Sabbath to see what new avenue they would open next. There might be stoner rock, doom metal, or in the case of FX, just a troll song.
Granted, it's not like Sabbath haven't done tiny snippets of songs before. On masterpieces like Master of Reality, there were songs like Embryo and Orchid which provided a nice pretty background before going into the heavy stuff like Children of the Grave. Right before we get into the song Supernaut though, we are treated to a solid minute and a half of what sounds like Tony Iommi just screwing around with a bunch of guitar effects.
To be fair, naming a song FX and having it be nothing but you moving a wah wah pedal up and down may have been a bit of troll humor at the time, but this isn't the kind of thing that you want to put on your finished album.
By comparison, this is the kind of interlude that makes you confused before going into the next track. And when one of your songs makes the audience got "what in the hell was that," you're not exactly getting invited to the Grammys or anything.