The insect that truly inspires fear in me are yellowjackets. I got stung when I was younger out washing my car and had quite a reaction, including major swelling of my arm that stayed like that for 3 days, and a bit of fever. It was so incredibly painful too. They sting so easily and in the late summer/fall they are out in droves and they just get up and buzz right in your face and they freak me out. I haven't been stung since then but I'm such a wuss about it and I really fear it.

As far as being disgusted/getting the willies, probably roaches. I remember when I was growing up in southern Missouri, you could turn on the light in the garage at night and there would always be a roach or two scuttling off into corners, just made me shudder. I know they don't physically hurt people but they just give me a feeling of disgust.

Ticks I believe are actually in the arachnid family and not the insect family, but they are another creature that causes a feeling of revulsion.