For me it is a tie between chaurus and hagravens...and I agree, a lot of it has to do with the slippery clicking noise they make (just like how I cannot handle dread zombies in Oblivion--the noises they make make me want to run away).
I also remember going to Orphan Rock in Skyrim on the quest for Nettlebane and being peppered by all these fireballs by some foe that I could not see. I was expecting some sort of mage, but when I made it to the top of the rock and saw a hagraven for the first time, I dropped my controller (and died)!
I would willing face a legion of frost trolls instead of these two creatures!
I don't know about that!
For me, the real scares come from the game's audio design. It might sound strange, but I've had more jump scares playing the last two Elder Scrolls titles than I have from any dedicated horror game. Playing sneaky characters with the music off, I'm constantly being startled by enemies seemingly attacking from nowhere. It's actually become part of the appeal to me, so much so that I won't use any detection spells or shouts.
For me Dragonborn DLC ash spawns... they are the ugliest things ever. Scariest: probably Draugr first 10 minutes of my first time playing I saw Bleak Falls Barrow was like okay then. I followed Arvel down into the crypt and... I had to buy new pants and died in-game, I was sad. Now they don't bother me at all!
Draugr. I think i am pretty alone for this matter but I think most of the people aren't scared of them because they are so easy to kill and there are many of them. But if you think about it: you are in a dark cave and there is nothing around you and suddenly BAM! stinky old dead person with blue glowing eyes!
Skeever's are the creatures that I find the most vile, overgrown rats carrying diseases, and the seem to always find a way to sneak up and then fill the whole screen with their jumping attack scaring the living daylights out of me. I would have to say they creep me out the most.
Scariest and disgusting - Werebears for scary and disgusting, especially when a certain glitch happens where the werebear loses its head, its limbs become long and twisted, its legs look normal but when it runs at you, Talos protects! The sight of it made me piss myself, I ran and ran but still this gangly headless horror followed me almost throughout Solstheim... I ran for help but it ended all the same... Everyone that tried to help met a fate worse than death...