PC:
ALL WEAPONS:
WALK one step forwards, one step back, (let go of walk) turn around 3 times in any direction, and do a backflip.
SKIP LEVEL:
WALK one step forwards, one step back, (let go of walk) turn around 3 times in any direction, and jump forwards.
PLAYSTATION:
ALL WEAPONS:
During play, go to the inventory & press look, draw guns, sidestep right, sidestep left, sidestep left, sidestep right, roll, and then look.
SKIP LEVEL:
During play, go to the inventory screen and press: sidestep left, sidestep right, look, roll, draw guns, look, sidestep right, and then sidestep left (Lara will sigh if it's done right), then press select and the level is complete.