Your mum
Sorry about the bad joke. Anyway
Has everyone here forgotten about the Tesla Cannon? I hear tons of people saying Deathclaws and Albino Rad Scorpions, but those scorpions only have 1500 health, and the Tesla Cannon does almost 1,000 damage and takes only 1 EC Pack per shot which means its wonderfully ammo conservative. Deathclaws only have 500 health. Both enemies are killable by 1 or 2 shots from the Tesla Cannon. If you have max Energy Weapons and Big Guns skill, I suggest you take the Tesla Cannon and take over the world because it's possible. Alien Blaster or Firelance works as well with their large critical chance and multiplier of the normal damage.
For me it's the Super Mutant Behemoth because of their horribly high melee damage which could easily kill my followers. I once again turn to my Tesla Cannon and hope I can get the shots on him quick enough.