Let's give the often-debated F3 farming issue a rest, but everything else is fair game.
Here's one:
In New Vegas, the PC meets Chris, a human who is helping the ghouls repair their rockets. Chris, being human, would be dead in minutes if exposed to the irradiated launch pad. But Chris thinks he is a ghoul; as far as he knows he is immune to radiation and could safely enter the dome. But he repairs the rockets, which implies on-hand experience, doesn't it? So, how did the ghouls get their rockets repaired by someone who couldn't touch them? Also, how did they convince him not to enter the pad without letting on that (they know) he is actually human?