For me it wasn't so much how they looked, but it was thinking about the process involved in making one.
In other words, making a human like that.
Still gives me the heebie jeebies to this day. :bonk:
I never thought of them like that, I guess I just can't wrap my mind around how a human can become that...
By the way, I looked at the Vault and a picture of them starring right at you is scary as hell... http://fallout.wikia.com/wiki/Failed_FEV_subject, if you dare!
EDIT- Apparently they were supposed to be an enemy only in Vault 87, I wish they were and that they were a lot tougher than supermutants because when I walked in their with Paladin Cross, Dogmeat, and then Fawkes we were invincible.