During gameplay, press START and enter any of these codes:

Sword Upgrade - Hold L1 + R1, CIRCLE, SQUARE, CIRCLE, TRIANGLE, TRIANGLE, SQUARE, CIRCLE, SQUARE
Complete Current Mission - Hold R1, SQUARE, SQUARE, SQUARE, CIRCLE, Release R1, Hold L1, TRIANGLE, TRIANGLE, Release L1, Hold R1, SQUARE, SQUARE
Big Heads - Hold R1, TRIANGLE, TRIANGLE, TRIANGLE, TRIANGLE, Release R1, Hold L1, TRIANGLE, TRIANGLE, Hold R1 + L1, TRIANGLE, CIRCLE, TRIANGLE