Serious Sam 2

Serious Sam 2 cheat codes: 
Start game as usual, open up the console with [~] key
and enter the command below (CaSe SeNsItIvE):

sam_iEnableCheats=1

Once enabled, close the console (press [~] again) and bring up the
mainmenu by pressing the [Esc] key - now you can enable the basic
cheatmenu by pressing [F1]. Repeat as often as needed just remember you
have to be in the mainmenu [Esc] to trigger the cheatmenu with [F1].

If you want to use the developer cheats simply use the following
command instead:

sam_iEnableCheats=2

You can also Disable the cheats with:

sam_iEnableCheats=0