Not Mutliple choice?
Voted Troll, but, as for "scare me".....well, playing the "Let there be Darkness" mod, anything within a Alyeid ruin that jumps out of shadows scares me.
Trolls, lichs, skeletons, wraiths (they scream at me), undead and necromancers can give me a good scare.
From SI -- everything scares the crap out of me -- skinned hounds, flesh atronachs, even the Ordered Knights...*shiver*
If you're voting on what creatures are a pain to kill, well Ogres take forever to die and Daedroth are just as bad.
Most hated critter? Goblins. The damn things are everywhere, in every cave.....screaming and yelling, until I shove a fireball down their throat. :flamethrower: