To get all the guns and full ammo, walk one step forward, one step backwards (you must use the Shift key), then turn around three times counter-clockwise, then jump backwards.

To obtain 5000 rounds for the Uzi, 87 shells for the Shotgun, and 500 bullets for the Magnum - In the beginning, walk forward once, walk back once, turn around three times (where you face your forward direction) and flip backwards. You should hear a faint click to confirm the code.

When Lara is hanging from a ledge, hold the WALK button and press UP to do a handstand.

To skip the current level, walk one step forward, one step backwards (you must use the Shift key), then turn around three times counter-clockwise, then jump forward. This is a great way to see the FMV clips.

If you win the game and reload any saved level you'll have all weapons, unlimited ammo and more enemies to defeat.