I happened upon the below video on YouTube. The video is of an Argentian man showing off the custom Franchi SPAS-15 shotgun he competes with in IPSC. The gun features a huge muzzlebrake that resembles a large mallet in size and shape. The magazine is custom and holds at least 18 rounds of 12 gauge shells in a single stack. It even has spring-loaded kickstand that automatically swings back when the gun is picked up off a stable (shaving microseconds off the time it would take to complete a course of fire).
Now I am skeptical about how effective the large muzzlebrake is, and I would not want to have such a large magazine getting in the way, but I applaud his efforts putting together such a unique gun.