I wasn't really phased by vault 34, although I walked past the reactor door and WAS NEVER ABLE TO FIND IT AGAIN :angry: . I spent like 10 minutes trying to get back to reactor door, and the local map was no help. Eventually I decided to give up and just leave with the pulse gun.
The scariest Vault for me was vault 22. Even though after you realise where the carriers come from and that you can see them. I just hate them, their posture and their heads they just look too wrong. So I always go in with a high repair, in and out with very little interaction. Even looking at their bodies when they are dormant before being disturbed, knowing that they could get up and charge is just.. urggh.
The scariest game in general for me is Condemned, the breathing noises of the enemies plus your torch being flickery, I have never been as scared by a game. Especially in the abandoned shopping mall with the half mannequin half human enemies. Walk past mannequin, turn around it's either gone and you might hear some shuffling, or it's standing there with a weapon raised inches from your head.