First bring up the Dev console during gameplay with: CTRL + ~.

Effect	Code
Dumb AI	cvarAdd g_inhibitAi 1
God Mode	cvarAdd g_permaGodMode 1
Infinite Ammo	cvarAdd g_permaInfiniteAmmo 1
Unlock perks	DebugUnlockPerkByAbility -1
Unlock perks 2	DebugUnlockPerkByRequirement -1