Anything that flies. Smaller non-flyers are alright, but for god's sake, anything that flies creeps the shit out of me.
I tolerate spiders because they eat those bastards...as long as said spiders don't get near me.
Aha, here we go.
I have my limits, and can deal with most of them, as long as they aren't too big. That being said one of the worst feelings that makes my skin crawl is having a spruce bug on you. The one in the video is a female, or male, I'm not sure, but I know one of the genders grows much larger than the other, and one has a set of nasty god damn jaws. They're strong enough that they can take skin off and leave scars if anyone ever let them go deep enough.
I hate the feel of their legs, they stick to you real easily, it's like you've got to tear the thing off you, and they make a horrid sound when you hold them. Not the ugliest or creepiest, but there's something about them that makes my skin crawl, worse than the largest spider could.