For whatever reason, wasps.
I hate wasps, every year at least one wasp finds its way into my house. I've got a "You don't come near me, and I don't wage an all out chemical war on your entire nest" deal going on with wasps.
And as for mosquitoes, I have two older brothers, and one day the oldest brother went outside for about an hour. By the time he came back inside he had killed about 30 mosquitoes and had a lot of bites on him. The funny thing is though he hasn't been bitten since, and that was over 5 years ago. My other brother and I joke that the mosquitoes are afraid of
him now, that he has the scent of death on him.
For a more irrational fear I used to have, I used to kind of be afraid of Ms. Frizzle from The Magic School Bus. I had a nightmare when I was about 6 that a volcano erupted while I was riding in a school bus. All of the sudden, the driver turned into Ms. Frizzle and she slapped a "lava-proof" suit on me and shoved me out of the bus to get us unstuck from the magma. I actually swam in the lava for a bit before waking up. Now I just regard any crazy person with a respectable amount of caution.