Most disturbing areas/moments

[Viking]

Pretty much what Commando Peach said about

Spoiler below!

Any running away bits. The initial water lurker section was terrifyingly tense as it was something new that happened.
After that, although there will still some really scary parts I started getting used to the mechanics of the game and realise monsters just disappear after a while after you've hidden for a bit (in most cases)

But then later on having to run away from the shadow and then find a door blocked with rubble! Gah! Physics help me!

Apart from that the other parts that made me jump and swear were

Spoiler below!

After going through the secret library area and getting back to the hallway, you spy a grunt walking through a doorway entrance. I went the other way and returned to the now caved in entrance to that library part only to turn around and find a grunt right in my face that suddenly disappeared in a puff of smoke. I screamed out such expletives at that point!

and

Spoiler below!

Returning to the Chancel the second time only to be jumped by two grunts as soon as coming through the door. I knocked my mouse off the desk at that point.

Don't know if they count as disturbing but they made me crap myself!