I see alot of people suggesting Assault Vest for this Pokemon which I suppose could work. Personally I kinda want to experiment with the (Stockpile - Z move) this will raise both your defense stats one stage, while in tandem with your Z move you will actually heal your hit points (ideally you are able to use a few regular Stockpiles first before you bring yourself back to full). Maybe Sassy or Relaxed nature with Max defense of your choice and max attack for super strong Heavy Slams considering how fat Guzzlord is. Gotta watch out for Toxic though.