Edit the "WillowGame.ini" file in the directory: "\..\Borderlands\WillowGame\Config". Change the value of the following lines in that file to activate the cheats.
Effect Effect
Cannot drop below 1 health point - Set "bDemiGodMode" to "true" Weapon slot capacity - Set "WeaponReadyMax" to 2 to 4 Increase maximum inventory - Set "InventorySlotMax_Misc" to a higher number Shoot own teammates - Set both entries of "bIgnoreFriendlyFire" to "false" NPCs can damage each other - Set "bIgnoreNPCFriendlyFire" to "false" Bosses do not regain health after dying - Set "bBossesRegenHealthOnReset" to "true" Resurrect all players when someone dies - Set "bResurrectAllPlayersWhenOneDies to "true"