Typical wet flies will serve you well, I would add Sedgehogs and hoppers in black, claret and orange. I have found orange flies work well in peat stained waters. Would also take some muddlers and a few Deer Hair Emergers (DHE). To be honest the list of flies worth taking will be almost endless.
Most lochs are going to have fish and be worth a cast. Will you be grabbing a quick cast whilst on a family holiday or is this a dedicated fishing trip? Are you looking for waters that require a hike to get to or something roadside? Do you prefer a boat or bank?