8. Cerebus - Dante's Inferno
Dante's Inferno has some of the most unique and disturbing boss designs in video game history. This is shown especially well in Cerebus, the many-mouthed beast that resides as the boss of the gluttony level. It would have been entirely easy for this boss to have just been a gluttonous, giant, or otherwise something resembling a mix between Dark Souls 2's Covetous Demon and Jabba the Hutt.
Instead, the three-headed Cerebus is an entirely different kettle of fish, breaking out of a huge beheaded corpse in order to try and chomp you down.
In a brilliant move, Cerebus' gluttony is also its downfall, as in order to finish off each of the heads you need to be eaten by them, so that you can destroy it from the inside, dramatically exploding it.
Even after you do this to one of the other heads, those remaining don't seem to learn the error of their ways, as they continue to do their best Chomp-Chomp impression in an attempt to catch you. You can hardly be mad at them, though, because it makes for a much cooler - and much simpler - battle.