Start a game. Press Back during a game to display the main menu. Then at the main menu, hold L + R + click Left Analog-stick + click Right Analog-stick, and quickly press White, Black(2), White(2), Black. A cheat option will appear.
The cheat menu will have "All Weapons" and "Refill" (restores ammunition, painkillers, and bullet time) options. To use these cheats, press Back during a game and select the desired options at the cheat menu. Then, press Back to resume the game.
Note: Other cheats in the cheat menu must be unlocked during the game.
Additional difficulty settings
Successfully complete the game on the "Fugitive" difficulty setting to unlock the "Dead On Arrival" and "New York Minute" difficulty settings.
Successfully complete the game on the "New York Minute" difficulty setting to unlock a new bonus level where you have to kill a lot of enemies, all in bullet time.