This was one of the most interesting things in Quake Expo 2006:
Video of it I uploaded:
It uses Gyro physics obviously:
Now this was on the page and it said something about Vengenance R2. Unforunately, the site doesn't seem to be operable any longer so apparently nothing will ever come of this.
I can understand the getting knocked around thing, I've seen the Quake airgun that can blow around health boxes and armor.
I've played with Gyro physics before and the floating, but in the video how are they getting brush models to rotate when impacted by the rocket?