I have a severe case of arachnophobia and a phobia against insects in general, which i've gotten alot of crap for, seeing as im a 190cm tall dude weighting in at 125kg, so to put it short, im a big dude, yet i cant stand insects/spiders/butterflies.
I'll give an example of how severe it actually is, a couple of years back, i had forgotten to close my window one day, and when i came back out to my room after watching tv for a while, there were 2 butterflies flying around near my roof lamp, making noises and stuff, i gathered my courage and brought out a book to try and hit one of them out the window, i hit it, it made a really loud noise, then it started to fly around like crazy flapping its wings really fast, i panicked, i had problems breathing and i slammed the door and ran away, once i had settled down in a "safe" place i started to cry.
I dont know why i panic when i see insects and such, i have no idea why i have this phobia, but i freaking hate it.