Yes! we use chainsaws, and are not ashamed to say it!
If you want to build a haunt to impress other haunters, then the answer is no, it will cost you points among the creative originality class.
If you want to provide good entertainment to your customers, then it's hard to beat the bang for your buck that you get from a chainsaw. Even the customers that are not scared by the saws, will get a good laugh from watching thier girlfriends bury thier face in thier arm and scream.
My take is this, there are really very few among us who have invented something completely new. Most good scares are a spin off of something that has been around for years. I have never seen a haunt that is composed of nothing but original props and scare tactics.
When an effective tool that is readily available and cheap is put on the shelf, I believe that you are imposing a senseless handicap upon yourself.
The only way I would not use chainsaws (note the plural) is if they did not fit the theme of the attraction.
BTW lawn mowers work pretty good too