Easter Egg Weapons:
Enter the following codes at the password screen:

     DYPYFASRHR -- All missions completed, all easter egg weapons. 
     SYMRGOBRRL -- No missions completed, all easter egg weapons. 
     DYSIFASRHY -- All missions completed and locked, all easter egg weapons. 

Passwords:
Level - Password

     1 - TAFRGYBLRR 
     2 - CRGRGYBLRY 
     3 - FUMRGYBLRL 
     4 - SICUGYBLLI 
     5 - TAFUGYBLLR 
     6 - CRGUGYBLLY 
     7 - FUMUGYBLLR 
     8 - SIFYGYBISR