The Big one - In'youchuu style tentacle

You know which one it is, you didn't just come here by chance, you saw it and said "I know that one!" yes it is, its the big one! The one that defies all basic studies on biology, the one that ignores the basic composition of the human body and organs... from that ridiculous hentai series to illustrious, there are no words to describe it, it's simply the BIG ONE.