To View the FMV sequences:At the title screen, press Start then enter: Z, A, Z, A, B, A, B, Y, C, A, C, A. You should now be able to see all the FMV's.
Refuel and reload your weaponsAt the title screen, enter: L, A, Z, Y, A, Down, Down. In order to refuel and reload, simply pause and resume the game while playing.
Level skipAt the title screen, do the following in this order: hold C, hold B, hold A, hold Up, hold L, release A, release C, release L, release Up. A voice saying "Blackhold engaged" will confirm that you have entered the code correctly. Then during the game hold A+B+C+Up+L at the same time to move to the next level or X+Y+Z+Up+L to go to the previous level.
InvinciblityAt the title screen, do the following in this order: hold A, Hold B, Hold C, release C, release B, release A, tap B, tap A, tap B, tap Y, hold X, tap Up, hold Down, release X, release Down A voice saying "You are on the wrong team" will confirm that you entered the code correctly.
Thanks to Revolution reader Limpy Carmichael!