The most value gear from caves are MK II, Brotherhood, NCR Ranger and Enclave Combat Armor sets, maybe some Metal Armor Mk II or Tesla can be usefull while playing against players with EW weapons or while farming Enclave (if you have no time to craft it, cave armors have no bonuses, not like crafted).
From weapons very valuable are H&K G11 and H&K G11E, especially for used by those guns rare 4.7 caseless ammo. You can find also Alien Blaster, Solar Scorcherer or Pulse Pistol which are very rare and good EW pistols too.
Oh, and sometimes you can find some rare and very powerfull Hypo. Somekind of buffed SuperStimpack