Serious Sam Codes -

Cheat mode:
Click and hold the and press , , at the main menu. A "Cheats" option will now appear at the main menu.

After enabling cheat mode, press during game play to access the cheat menu. You can restore you lives and ammunition to avoid dying.

Developer cheats:
Click and hold the and press , , (x3) at the main menu. This will unlock the "Cheats" and "Developer Cheats" options. The "Developer Cheats" will allow you to go to certain checkpoints.