Humanoids
Feral Ghouls
Feral Ghouls are humans that have been incredibly irradiated and somehow survived. The process of transformation has sent them insane. If they notice a human they emit a high-pitched moan and attack.
Strategy
Feral Ghoul - Two headshots from most guns, or a solid hit from a melee weapon will take them down easily, but keep your distance if you are a low level.
Feral Ghoul Roamer - The Roamer is a lot faster, does more damage, and takes more damage than the regular ghoul. The best way to deal with these is to cripple the legs and attack the head from a distance.
Feral Ghoul Reaver - Reavers are very, very fast and powerful so crippling their legs is paramount. They are also armored so the head will take most damage.
Glowing One - Glowing Ones have a dangerous radiation attack they use if you get too close, so keep your distance. Cripple the legs then go for the head.
Feral Trooper Ghoul - Trooper Ghouls are like Roamers, except they sometimes attack with knives. Use the Roamer strategy.
Glowing Trooper Ghoul - These are armored Glowing Ones and are really dangerous. Stay well away, cripple its legs, and as always go for the head.
Vault Security Officer - These are the same as Glowing Trooper Ghouls. Use the same strategy.
Vault 34 Overseer - The Overseer is very difficult. He has very high HP and the same attacks as the Glowing Ones. You should deal with the turrets in his room first, as they deal lots of damage, then cripple the Overseer's legs and arms, then focus all your attacks on his head.