press the ' button enter 'killcars' the vehicles will then respawn where they started
press the ' button to get the console and enter 'fly' to turn it off enter 'walk'
press the ' button on your keyboard which is next to the full-stop button, the command console should come up enter 'god' god mode will now be on and a sign should come up at the top of the screen.
press the ' button to bring up the console, enter 'invisible true' if you shoot to much the enemies will see you and if you got to close they'll see you. to turn it off enter invisible false
select machine gun, left click to deploy, press ' to get the console enter walk, warning: do not enter vehicles while walking with machine gun
Hit T then type: Behindview 0.
Hit T then type: Behindview 1.