I don't know about most people, but I was most afraid about death, especially when I was a child, just thinking about it used to bring me to tears. I have matured up since, and my knowledge about it has obviously become better - most definately in saying that I am not ready for it!!!!
Otherwise Spiders. And my partner when he is super, like SUPER mad. Haha. Luckily its never caused by me! ...i hope....... :P