I think the least scary one of the 5 would be the bullet ant. The fact that you know a tribe somewhere out there uses these ants as a ceremony into manhood, it takes away a lot of the scary factor of the bullet ant. From the looks of it, you don't die from their stings. It just hurts like a mofo, but you don't die, and you don't get poisoned or anything. I'll still be scared to see one though.

On a side note... I'm more scared of spiders.