High DT? Remnants Power Armor, or Gannon Family Tesla Armor, or T-51b Power Armor. Only one of those is actually unique (though they're all in very, very short supply) but they are the toughest things in the game. T-51b is the most balanced of the three. Remnants has the highest DT, but is a little low on durability (but it's DT is so high that it's rare for something to damage it in the first place), and Gannon isn't quite as tough as Remnants, or quite as durable as T-51b, but is right between them, and only counts as medium armor, so you can move pretty quickly in it. And it makes you extra resistant to energy weapons.