Invincibility:  Enter DEATHWISH as a password.

Unlimited ammunition:  Enter BIGPOCKET as a password.

All weapons:  Enter TOOLEDUP as a password.

One shot kills:  Enter OOHSTOPIT as a password.

Rapid fire for shotgun:  Enter MYBIGUN as a password.

Extra explosion damage:  Enter ACMEBANGS as a password.

Enemies less aware:  Enter COLDFEET as a password.

Invisible mode:  Enter DOYOUCME as a password.

Alternate sounds when hit or killed:  Enter HORNBLOW as a password.

Unknown:  Enter COLDFEET as a password.

Level Ecks Sever

2 SMOKEY RAVEN
3 BUTTERFLY FIREFLY
4 COVEY BULLDOG
5 TIGER DRAGON
6 HORNET LOUDMOUTH
7 LITTERBUG STINGER
8 MUSTANG NAIL
9 SPECTRE ZORRO
10 NIMROD XRAY
End SPOOKY REDDOG

Multi-player linkup:  You can link up a Game Boy Advance with Ecks vs. Sever and a Game Boy Advance with Ballistic: Ecks vs. Sever 2 and still play all the multi-payer modes. The level combinations between the games are slightly glitched, but it still works.