Assuming you have the appropriate DLC. I'm vanilla :P I suppose a Plasma Rifle would see them off easily, I pretty much used a Combat Shotgun/Assault rifle/Hunting Rifle combo for everything >_<
I specifically use the Alien Blaster for the giant radscorpions, not to mention a boat load of bottlecap mines. I hate these things as much as Morrowind's cliff racers, I just want them to vaporize as quickly as possibly without wasting ammo.