Press [~] during the game to access the console, then type in the following for activating the cheats:

cheat youbetterpay                      = 100,000 cash
cheat needmorelead                      = 1000 everything
cheat loonies                           = Crazy guy who can hold two tommy guns
cheat alienprophets                     = Fake cops
cheat wowitsgreattobetheboss            = God mode
cheat kidiseeeverything                 = No fog of war
cheat youwillbestunned                  = One assasin
cheat yourliverlandedoverthere          = One bazooka guy
cheat iwilltakecareofyou                = One big momma
cheat youhadbetterwearkevlar            = One black widow
cheat trustmewithyourlife               = One bodyguard
cheat likeatonofbricks                  = One bomber
cheat pocketsfullofdough                = One businessman
cheat iwillripyouramsoff                = One enforcer
cheat iwillmakethefamilyrich            = One lawyer
cheat iknowodintoo                      = One ninja
cheat youlittlehottieyou                = One seductress
cheat thegreatvassilizaitsev            = One sniper
cheat ihavetenpundfists                 = One super bouncer
cheat whatwasbrieflyyoursisnowmine      = One thief
cheat irissuxx                          = Yeah! message