i've tested the garry's mod controller mod in half life scouce sinse it users the same enging from half life 2 like G-mod it works for both single and multiplayer mode just install the link right here https://garrysmods.org/download/526/xbox-controller-config its virus free aswell but you can check if you want just place in the joystick.cfg file in half-life2\hl1\cfg and there you go after that turn on gamepad in mouse option in-game settings config keyborad settings and have fun