Depends on the class. Warlock: 1 Hunter: 2 Titan: 3 IMO. Warlock should rely pretty heavily on their Spagic, so they should probably only need one gun, since that's essentially two weapons. Hunter, obviously, long-range and mid-range or long-range and short-range. Titan makes sense to have three. They're probably the strongest of the Guardians and so it makes sense for them to have a Canon/Heavy weapon, a short range, and a mid-range in case their heavy is too slow for the current combat situation.