For me it's spiders. Funny how I used to play with 'em when I was younger, now they just creep me out.
Speaking of snakes ... I got this friend she is soooo afraid of snakes, she can't even look at a picture of one. She got the local university paper once dropped off in front of her door and it had a snake on it. She refused to leave her room. She had to call her boyfriend to come and get rid of the paper. It's funny for a short while, until you realize how serious it is.