Cheats:

Invincibility:
Enter NECROSCI as a code. Note: This has no effect when you fall from high places.

Never take damage:
Enter CHEATERBOY as a code.

All Gadgets:
Enter TINKERTOY as a code.

Secret Morphs:
Enter LOGGLOGG as a code.

All Morphs:
Enter EUREKA as a code.

Go anywhere:
Enter BEAMMEUP as a code.

View FMV sequences:
Enter HOTTICKET as a code.

Super ending:
Enter BUZZOFF as a code.

Hint: Easy Isotopes:
Zap the television in Muto's house to get 10 Isotopes.

For Walkthroughs Try These Sites:

www.gamespot.com