Mouthpiece has a few elements in his fight that I worked on that I was particularly proud of, and you may find interesting.
Equalizer Shield - Mouthpiece dons a shield that has a functional equalizer. The bars on the shield will increase and display the actual audio frequency of mouthpiece's voice as he speaks and attacks the player. This same equalizer effect is displayed on some monitors around his arena, and the material is reused on a unique weapon that he drops.
Speaker Attack - In the mouthpiece fight, there are speakers along the walls that will blare sound at the player enough to damage them during the fight. To telegraph the attack the neon tubes on the speakers fills up and the speakers employ a vertex shader to comically pull back then blast out the cone to visually compliment the sound attack. While this is not realistic, it is the kind of over the top animation we wanted for the fight and helps provide a clear telegraph of the attack to the players.
Video of the speakers in action