The House of the Bayou Witch
Position: Beginning to middle of house
A dilapidated shack, hung about with moss, creepers, and snakes (can't forget the snakes), is the home of an old lady. She has crazy grey hair that sticks out at angles, scruffy and layered old clothes, and stumps out onto the porch to shout warnings at the guests. She tells them that anyone continuing on will certainly die.
Then an alligator snaps out at the people from under the porch.
Technically, this is a very simple trick with a fairly low-tech prop. The alligator is no more than the front half with a mouth on hinges that is set to pop open. The more realistic this looks, the better, but scary is just fine. The prop is on a short rolling cart and the porch should be low enough to keep the mouth closed. While the old lady goes into her spiel, another actor (dressed in black) beneath the unlit porch takes careful note of where the feet are. He rolls the gator out quickly so as to miss any guests, and the prop does all the scare.
Lots of teeth are good.