Bull snakes are a barrel of funI kept a baby for awhile when I was rescuing, and he was definitely the craziest little thing I've ever had the pleasure of caring for. He would hiss and wiggle that tail against the side of the cage like a rattler, and try to scare me away every time I reached into her cage. All bluff though... he struck a few times, but always just bumped me with his head. Never bit.
They can have attitudes, I guess is the morale of the story, but that's really the only "danger" they present, and can be very fun and rewarding to keep.
I'd check on your local wildlife collection laws, though, before catching one and keeping it. In some places, it's illegal to do so with bulls. Getting one from a breeder would be a better bet. Just my two cents.