The Incinerator Cannon was the only Forerunner weapon that I didn't have hands on time with, however I did witness it being used a few times. It is definitely similar to the rocket launcher, but it looks like it had a greater area of effect. After the initial explosion a few smaller particles are dispersed that create smaller explosions within a certain radius. I witnessed a few people kill themselves because of the splash damage, this baby is lethal. I overheard talk that the residual explosive particles are actually physics based, so you better be aware of your surroundings--I'm talking about teammate killing prone players. In fact, I believe one such community manager might want to take note.