Weapons cheat
Get a flare out of Lara's pack and light it
Move Lara one step forward
Move Lara one step backward
Rotate Lara around 360 degrees, three times (just keep your finger on the turn key)
Make Lara backflip

Level skip cheat
Get a flare out of Lara's pack and light it
Move Lara one step forward
Move Lara one step backward
Rotate Lara around 360 degrees, three times
Make Lara jump forwards