Level skip code:

Press the slsh key (/) so that Lara will draw a flare. Now, walk one step forward, take one step backward, turn around 3 full times, and then jump forward.

All weapons code:

Press the slsh key (/) so that Lara will draw a flare. Now, walk one step forward, take one step backward, turn around 3 full times, and then jump backward.

Blow yourself up:

Hold walk then go one step forward, take one step backward, turn around 3 times, release walk and jump forward. BOOM!!!!!!