Don't know if i should give props or call the cops: http://www.joystiq.com/2008/01/23/toy-chainsaw-nerf-gun-time-diy-gears-of-war-gun/
Oh man, I damn near pooped myself laughing at the end of the video when he chainsawed that kid. Best nerf gun ever.
He could have made a few extra changes while he was at it. Taken the flow inhibitors out and turned the bolt action into a pump action. That's a pretty popular mod in the nerf community.