Serious Sam: The Second Encounter

Cheat mode (demo version):
Press ~ to display the console window. Enter one of the following codes then press [Enter] to activate the corresponding cheat function.

Effect	Code
God mode	please god
Restore energy	please refresh
Flight mode	please fly
No clipping mode	please ghost
View all messages	please tellall
All weapons and ammo	please giveall
Kill all monsters on level	please killall
Open all doors	please open
Invisibility	please invisible

Alternately, select multi-player, then choose Serious mode and The Grand Cathedral as the level. Complete that and Mental mode will be unlocked.
tyruagviiosh.

Hint: Bad ending :
At the last level when you reach the giant after the bouncing arrows, enable the please god code. Then, do not kill any enemies. Go to the church. Enable the please fly code at the front door and go over the wall. Continue ignoring the enemies, including the wizard, and go to the door. Enable the please open code, enter, and wait for the rocket to appear. Do not press anything and watch the ending.
Bkggear.

Hint: Valley Of The Jaguar: Blue Armor:
Reach the door that leads to the female golden jaguar. Before entering it, look on the left side of the wall to find a bouncing block. Go on it to find Blue Armor.