Shoqiyqa said:I got the reference but that was more annoying than scary in my experience.Grouchy Imp said:"VENGEANCE!"
Cookie for the reference.
The call of dead king Lysandus in TES II: Daggerfall.
The scariest sound in that game was probably the moaning of an Ancient Lich. The b_____d things resist Dispel Undead.
Archviles sniffing around, looking for you, in DoomII spring to mind.
The combined engine noise, gravel crunch and metallic squealing of a tank coming your way when you know you don't have any armour in the area and you're not carrying any anti-armour weaponry is also kind of unnerving.
Everything in the large room respawning at once before you've finished the lever sequence to open the exit in Asheron's Call is a really bad sound.
Enemy Territory: *click* right under the foot you just put down.
Quake spawn waking up and starting to bounce around. Vile things!
Halo:CE's worst is either "Everybody duck!" as a little Covey git lobs a plasma bomb at you or that rapid, high-pitched sound the swarms of Flood mushrooms make.

It suppose it could be considered annoying once you've gotten used to it, but the first time you ever hear it? When it's about three o'clock in the morning, the only light in the room is the glow coming from the computer screen, and you're totally wired? Not an experience I'd like to repeat...