During the game, press ~ and type in restart, then press Enter.  Press ~ again to minimize the console.

Skip Introduction Sequence

Start the game with restart +1 in the command line parameter.

Scare Your Character To Death

Get in a jet and fly straight up until you cannot fly any higher.  Then, eject from the plane.  When you do bail, everything should be white and your character will scream as he falls.  After a few seconds, the screaming will stop and you will hear your character crap their pants.