Gotta say, I'm surprised the Falmer and their accompanying Chaurus didn't get their own option.
I fuggin' hate the Falmer so much! I hate the fact that they're blind, yet they seem to be able to see me, even though I've got 100 Sneak and a bunch of the associated perks, and am crouched motionless in complete darkness. (I know they're supposed to have heightened senses of smell and sound, but the game doesn't actually register detection based on smell, and like I said I'm completely motionless) I also hate the fact that when I was at a lower level, trying to do the main quest, I had to crawl on my stomach through a HUGE Falmer-infested ruin at a snail's pace because at the level I was at it would literally take 4-5 hits from any Falmer and I was dead, which led to me leaving the ruin, levelling up a few times, then having to do the whole sodding dungeon again with even higher-level Falmer in my way!
Also, a special mention goes to any mage-type enemy who uses a Ward spell. I usually open a battle with one of my shouts, so having that blocked then having to run up to the mage while they spew destruction spells out at me is pretty annoying.