The most sought after trick in magic is levitation. The next is vanishing something but I am not going to talk about that. I will tell you a little about levitation. The ugly secret is simple, some kind of support system is needed. Some magicians don't know the mechanisms needed to develop a great lifting apparatus (although you can ask any magician and they will all tell you how to build the best one). As builders, your challenged with restrictions like time, weight, sight, space, and others. I will say that an actor lift is perfect for haunts the one I worked on at Netherworld was like a seesaw counter-weighted in the back. This was perfect but there were space constraints. Imagine hiding a seesaw that's able to lift an actor about 3-4 feet in the air.
Pneumatics? They are used in illusions but not like you might think. They are not as well used as motors. The only time they are used are to lift very heavy objects like a car.
Motors. I developed an idea for levitating an actor who walked up to a cemetery gate. See the pic.http://www.homehaunter.org/levi-drawing.jpg Inside one of the gate poles is a drive shaft (not sure if you call them drive shaft poles) as it slowly turns it lifts a guide though a channel. The actor has a harness and a female connection that would allow the actor to just walk up, remotely start the motor, and left into the air with hands and feet free. This is not an original idea the same concept is used in this illusion called the pole levitation. http://www.youtube.com/watch?v=o_LyCTFMrMo The screw shaft is attached to the motor and slowly turned:http://www.homehaunter.org/lift.jpg
There are motorized lifts that can do levitation but many of them (if you buy from magic dealers) are very, very expensive. These magician motors also move way to slow for a good scare anyway. Most of these motors are taken from old dentist chairs and then re-sold for illusions.
Another actor lift that might be the best way to go if you don't have the space is a Genie lift. Yeah, I said the Genie lift. See the image.http://www.homehaunter.org/genie.jpg This lift can easily be converted into a motorized lift and stand on a flat metal sheet (with, or without wheels). The forks are removed and replaced with a square place for your actor to stand. If you're really creative, you can develop this idea to where all parts can be replaced. This way you can use it to scare guests and then pack up your haunt when the season is over.