I dressed up as Leatherface for Halloween in '05 and used an old chainsaw minus the chain to scare people at 2 parties I went to.
Me with my Saw
My costume on its own (without the saw) worked well enough that the two spook houses I went to offered me a job that night if I wanted it, mainly because I scared the people working in the spook house, and that their Leatherface was essentially a mini-me when compared in size.
Me and the Wife
I'm 6'8" and at that point was about 440 lbs (lost almost 100 since then) and I had some platform shoes I wore to another party where I was easily 7 feet tall.
I ended up using a super long Welding Apron because that was the only thing long enough to fit me without looking ridiculously tiny. Most aprons ended up looking like large bibs lol.
I scared the crap out of people at both parties. I'd show up, start the chainsaw and charge in. Then I'd wait an hour or two and do it again to mess with the new arrivals.
My buddy made an actual, functioning Freddy claw out of copper pipe, rivets and metal from a machete, he said working with the steak knives just wasn't worth the time and wouldn't look right. Cost him about 2 days of tinkering and 40 bucks to make a claw that people offered him $250 on the spot for. He turned it down and now has it on his mantle piece. He found a red sweater and spray painted the stripes and then dragged it behind his car. His face was done with just some wax, latex and his wife's old make up.
Me and my friend in his Freddy Costume
My friend as Freddy
Lessons Learned:
1. Chainsaws are oily and messy and lose the fun scare factor after the first one or two times. They are a royal pain to cart around in anything other than a pick up truck as they get everything oily and gassy. Just the gasoline stink and oil stink alone is enough to drive you batty, especially if you have to ride in a car or SUV with it.
2. I am an ogre but even I got tired of lugging it around, unless you're out swinging it around etc it is just a glorified prop, and a bloody prop machete, knife, mallet or hatchet works just as well if you have to carry something.
3. Unless you plan to be scaring kids on your property or a fun house, it just isn't worth it to carry around the whole time. The other thing is having stuff in your hands sucks because invariably you have to take off your mask to get some air, drink a beer or two and you either have to juggle the prop and mask in your hands or set it down etc. They look great but become a pain in the ass quick. Do the scares and then stash it and get to partying.
4. I got a chainsaw and leather welding apron for a costume and have ended up using them for odd jobs around the house and yard. The leather apron still has the 'blood' stains on it but it is great for when I am working on my guns, knives, swords etc.
That said the cops in my town seem pretty cool compared to how uptight the people in this thread are, they wanted pictures with me and my friend in the Freddy costume. Course it is a college town (Stillwater OK) and the crime rate was pretty low. The year before I walked onto campus in a Jason costume with a bloody machete in broad daylight and no one cared. Most people excuse craziness on Halloween that any other day of the year they wouldn't put up with.
You can tell if a chainsaw has no chain on it or not, and unless you're wandering around at random people or bringing it into public settings like a restaurant or store it isn't a big deal. The point of trick or treating is there are supposed to be tricks, like scaring the crap out of kids, or giving them ice cubes instead of candy, or asking them to answer questions (like who was the first president or 5 times 10) if they want candy. I would say don't go wandering off your property, but instead use it to scare kids that walk by etc.
I've had people pull the no-chain chainsaw trick while out trick or treating quite a few times. Kids and adults love the sound it makes, there is no mistaking that noise in the dark. Thing is it is a Halloween only deal, when cops and people are expecting scary silly crap. Do the chainsaw trick in say middle of November or September and prepare to get yelled at.