SON OF SAM: All items
MURDERER: All weapons
BRUCE: Invincibility
NICK: Max health
CHARLES MANSON: The Lodge - Final level
DUSTIN or DUSTBIN: The Lodge - Level 1
BOSTON STRANGLER: The Lodge - Level 2
HELTER SKELTER: The Lodge - Level 3

Just type them in. You will hear a shotgun go off if done correctly.