Code:
local wireframeMat = Material("models/wireframe");

GAMEMODE:AddHook("PreDrawViewModel", "", function()
    if(!gBool("Visuals", "Wireframe Viewmodel")) then return; end
    render.MaterialOverride(wireframeMat);
    render.SetColorModulation(0, 0, 0);
end);

GAMEMODE:AddHook("PreDrawPlayerHands", "", function()
    if(!gBool("Visuals", "Wireframe Viewmodel")) then return; end
    render.MaterialOverride(wireframeMat);
    render.SetColorModulation(0, 0, 0);
end);