Harrison Krix, the brain behind the Portal Gun and a number of other videogame replicas has just begun work on the Zero Point Energy Field Manipulator, better known as Half-Life 2's Gravity Gun.
Wielded in both hands by Gordon Freeman in the game, this replica of the Gravity Gun is designed to be a life-scale model of the device.
More of Harrison's work can be found at his website, Volpin Props.