Unlock Everything
On the press start screen (seen before the main menu press the following key configuration in order). If the cheat is entered successfully you should hear a gun shot. Note: PC in brackets are the default controls. If this doesn't try it with cursor keys for left and right. Enter: Coverpoint (Space), Right (D), Right (D), Left (A), Left (A), Change Weapon (Q).

Cheat Mode
Press [Space] DDAAQ at the "Press Start" screen before the main menu appears. The sound of a gun will confirm correct code entry.

Alternately try with cursor keys
Press [Space] [Right] [Right] [Left] [Left] Q at the "Press Start" screen.