Players can utilize the following cheat codes in Half-life: Opposing Force single player games. To enable the cheat codes, start Half-Life using "hl.exe -dev -console -game gearbox. In order to make this work, you may have to modify the windows shortcut properties for Half-Life: Opposing Force and adding "-dev -console -game gearbox" to the end of the target's filename. (ex. right click your shortcut, click properties, then modify the target entry with the bolded script.

Once you have enabled the cheat mode, press the tild key (~) on your keyboard to bring down the console, then you can access the codes listed below by typing them in to the console.