Level Skip Code : 
While in a level do the following with Lara: 
Press the Forward Slash key (/) so that Lara will draw a flare. 
Now, walk one step forward (hold down the walk key 
and press the up arrow), take one step backward (hold 
down the walk key and press the down arrow), turn around 
3 full times (doesn't matter which direction), and then do a 
Forward jump. 

All Weapons Code : 
While in a level do the following with Lara: 
Press the Forward Slash key (/) so that Lara will draw a flare.
Now, walk one step forward (hold down the walk key and 
press the up arrow), take one step backward (hold down the 
walk key and press the down arrow), turn around 3 full times 
(doesn't matter which direction), and then do a Backward
 jump.