I have a special spider scream, no other thing on gods green earth causes me to make such an undignified noise!
It is highly embarrassing and only happens when I am confronted by a spider.
It goes a little like this oooaaahaahhuuuuurrrrgggaaaa and is usually accompanied by a strange little 'pony cantering on the spot' type jump 
The bigger the spid, the louder the noise and the bigger the jump.
The worst thing is that's it's completely involuntarily - I even do it in public without realising 
Last night I dreamt about a big spider on the ceiling above my bed, I woke up to find myself butt naked and cowering on the other side of the room, demanding in a very loud voice that DP turn the light on so I could see where the bastard was!
Totally irrational - I know there's no spider, it's dark so I wouldn't have been able to see it anyway, nevertheless it happens on a regular basis!