During play, press ` to bring down the console and enter the following cheats:

 
god                 God mode 
godteam             Team god mode
godterro            Invincible terrorists
godhostage 1        Invincible hostages
godhostage 2        Disable invincible hostages
godall              Turn on every god mode
behindview 0        Toggle third-person view
behindview 1        Toggle third-person view
ghost               Flight mode

walk                Disable flight mode
fullammo            Full ammunition
togglecollision     No collision detection
resetmeall          Reset all cheats

Thanks to Revolution readers MILL J, Kenny and Grim Reaper!