DD8B-6DA4 Start with 1 life instead of 3
DF8B-6DA4 Start with 2 lives
D78B-6DA4 Start with 4 lives
D08B-6DA4 Start with 5 lives
D68B-6DA4 Start with 9 lives
DE8B-6DA4 Start with 16 lives
F38B-6DA4 Start with 31 lives
3C8E-DDD7 + 3C8E-DD07 Infinite lives
DFC3-DF0D Start with 1 credit instead of 4--use for 1-player game only
D4C3-DF0D Start with 2 credits
D1C3-DF0D Start with 6 credits
D5C3-DF0D Start with 7 credits 
D6C3-DF0D Start with 8 credits
DBC3-DF0D Start with 9 credits
C227-6DDD Infinite credits 
DFBB-A766 Makes Earwig Scorpion (Stage 1 mayor) much easier to defeat
DFB1-6F6C Makes Bubble Brain (Stage 2 mayor) easier to defeat
3C29-0704 + 3C29-0764 Weapons status gauge remains at current level after a 
weapon is selected
CBAF-D7AD + DFA4-DDDD Enemies shoot at you more