I know it's been a while so here are 3 little goodies to get those gears turning in your half eaten brains. I haven't built any of these yet, but I might soon.
The first idea is your standard corner shelf unit that can either be found in the kitchen, dining room or the bathroom in your haunts. These units normally have 3 to 4 rectangular shelves.
I figure you can trim the bottom shelf round so it can rotate on an axle with ease. Use the extra cut-outs to glue them in place on the unit. This will make the shelf look triangular when it is not (that's kind of hart to write but look at the drawing). he dotted line shows the trimmed boards and support shelf for the actor. No motor or air needed. The actor inside can move the shelves over and jump out. He can then climb back in and rotate the shelves right back again. This shelf unit can be found at almost any rummage sale so keep your eyes open. I think the better way to do this scare would be to use a corner shelf unit that has the cabinet door below. Like in the picture. This will give the actor a bigger scare.
The second idea here is something I am very familiar with. In magic and illusion. Magicians use "cars" to vanish or appear or levitate. In any case, more often than not, these cars are shells. Just an outer body of fiberglass is seen with real tires. They are even strong enough to roll off and on stage. The good news is they can be lifted by two people. There are illusion builders like Bill Smith who can make them (or at least point you to someone who can). And they may not cost all that much. carshell.jpg
The idea is your gusts see a monster destroying a town. Their path takes them closer to the chaos nearing a car for cover. The huge monster swings his hand at a car and the it flies off. Turning in the air only to land over the heads of your guests. With the right sound (horns, crashing glass and lights) this should be very effective. You'll need time to work out the kinks with the motorized arms (or pneumatic). This sounds like something Unit 70 guys will do.
The last idea is something more interesting than anything. I saw this video on youtube:http://youtu.be/3zoTKXXNQIU It's just corn starch on a speaker. In the video, the corn starch lift up slowly like a movie special effect, almost like bubbling flesh. In real life, this could be shocking if found inside a moving body. How? Well, again these are just ideas and it will take some trial and error. I think you can just cover the speakers with some very taught rubber like latex and then use colored corn starch. Maybe use a body that is stuck in transform mode from human to zombie.
I hope I sparked your imagination a little with these ideas from my black book. I will be posting some more very soon