Serious Sam II cheats and cheat codes for XBox

Go to the main menu and hold the R trigger, push Black, White, Black, White, 
Black, White buttons on your controller repeatedly until the cheats option 
will display at the bottom of the screen.

After that, push the X button to access to the cheat menu.
When you activated a cheat, you will see a message.

Armor in Lava stage
Before you pick up the mini-gun, enter to the door on your right side. 
You will see an armor on the other side. 

You must to step on the correct letters in order:
S, E, R, I, O, U, S.