All Weapons Code:
Press Select to enter inventory screen.
Press LOOK, DRAW GUNS, STEP RIGHT, STEP LEFT, STEP LEFT, STEP RIGHT, ROLL, LOOK,
You should then have all weapons

Level Skip Code:
Press Select to enter inventory screen,
Press STEP LEFT, STEP RIGHT, LOOK, ROLL, DRAW, LOOK, STEP RIGHT, STEP LEFT,
The level will skip.

Level Skip Code:
While playing do this carefully:
Using the WALK key, take one step forward,
Take one step backward,
Turn around 3 full times (3x360^o in any direction),
Do a forward jump while still pressing the direction key.
The level will skip.

All Weapons Code:
Using the WALK key, take one step forward,
Take one step backward,
Turn around 3 full times (3x360^o in any direction),
Do a backward jump while still pressing the direction key.
You should then have all weapons