I have a bullsnake that's quite a little devil. As soon as you take the topper off of his tank, he's hissing and striking at the sides of his tank.
My dad and I had it out last week, and it went straight for my face, started hissing, growling, and shaking its tail like a rattler. It was .. precious.

And, my newest BP, Adrian. I'm her fourth owner and her first correct husbandry, so I can understand that she's shy. She hisses and slithers around .. then sits in her water bowl for a few minutes.