A drill is all tthat comes to mind......
Industen, a few years back I made something very similar to what you are talking about. My first attemps failed miserably. I'd like to make one suggestion for you if you are planning on having this character suspended from an arm extending from the center post. Balance your load. In my case I used 2 grim reapers. one on each side of the beam I was turning. It looked like they were chasing each other and it was MUCH easier on my motor. It is hard to believe how much of a load it creates if you have an unbalanced load. Ended up destroying 1 gear motor before I figured it out the hard way. In your case a counterweight might be the answer. I used a lazy susan bearing at the top of my shaft and it worked out great.Think of a big piece of PVC pipe with a smaller size in the center, the bottom of the smaller will be capped and connected to the motor about 1/2 way up. This will spin the smaller PVC which will come out of the bigger and extend outward about 2-3 feet.
The larger PVC will be secured with a T or 4 way enbedded in concrete. Then I can just slide it over during the haunt season and cap it off during the rest.