Amok

All these are typed at the password screen:

Mission 2, Phase 1: CBYXYC
Mission 3, Phase 1: XABXAB
Mission 3, Phase 2: AZCBXC
Mission 4, Phase 1: YYBBCY
Mission 4, Phase 2: BAXCXX

Enable Level Select: ZZZCYX
Show Credits: ZAZACC
Invincibility: BABYXX.
Rapid Fire: YAYAYA

(Information from Cheat Machine)