You have your costume all together, but you feel like something's missing; maybe you need a couple of Halloween props to complete your look and make your Halloween presence unforgettable!
The Collecting Bag
Consider your trick-or-treat bag. Nothing wrecks a character's believability like a princess carrying a grocery bag or Spiderman with a plastic pumpkin. There are so many options available for collecting that there's just no excuse for "making do" with a pillowcase. Witches and wizards should consider collecting in a cauldron. The headless horseman could collect in a "head" or skull. Skeletons, zombies, and mummies can use skulls as well. Comic book heroes can choose one of their trademarks -- or at least color-coordinate their collecting bag with their costume color. What about Spiderman with a cotton mesh shopping bag -- those things look like they are made of spiderweb!
Masks can be the making, or the undoing, of a good costume. If you are good with greasepaint, a mask might not be needed. But if you're not talented at makeup, there are many options available at most party and costume stores. Vampires need vampire teeth, of course, and a trickle of blood dripping from the corner of the mouth is a good addition. Corpses, monsters, and scary things can use the many rubber scars and wounds carried by most costume shops. A fairy with an unmasked face isn't nearly as entrancing as a fairy with an elaborate feathery mask.
Other Portable Props
For carrying with you while trick-or-treating, you don't want too many accessories weighing you down. But a few spiders, bats, or bloodstains can be incorporated into a costume or collecting bag without difficulty. If you're planning to carry a light for safety reasons, consider camouflaging it by turning it into a ghostly companion or a will-o-the-wisp. If you must take a vehicle (car, wagon, baby stroller, etc.), then by all means drape it with stretchable spider web and a few plastic spiders, and maybe put a lighted plastic jack-o-lantern over the hood ornament. Rubber "body parts" can be effective on car grills or sticking out of the trunk.
House and Yard
If you aren't going to be carrying it around, the sky's the limit for more stationary decorations. Perennial favorites among home and yard decor include skeletons, bats, spiderwebs, witches, "smoking" cauldrons (dry ice is a wonderful thing), and scary noises played on an endless-loop recording. Carved, candle-lit pumpkins are almost required. For homes or cars, there are rubberized items that adhere to glass: bloody handprints and dripping blood are two of the most common.
Some party and decoration suppliers even have vinyl and cardboard backdrops to make "creating a scene" easier and less disruptive to the normal home decor. With various choices ranging from the merely spooky to the downright gory, there's something for every taste.
Standup Halloween Props
Some of the most successful Halloween props are the standup or animatronic characters. There are many different kinds available, from witches and mummies to zombies and Frankensteins. If treated properly by setting them in a place where they will appear to "jump out" at someone who crosses their sight-line or their motion detector, these Halloween props can be wonderfully effective at creating a scary, spooky atmosphere.
Food is a great decorative medium. Set up a "witch's pantry," with rugged board shelves containing labeled mason jars of peeled grapes ("eyeballs"), diluted ketchup ("blood"), chunks of white chocolate ("dragon's teeth"), cooked egg noodles ("brains" -- or ask your local butcher to get you some "sweetbreads, which are the actual brains of sheep or calves), unrolled fruit leather ("lizard's skin"), and so on. Make it more mysterious by setting up a "smoking cauldron" in front of it.
Where to Get Them
There are hundreds of fabulous places to get Halloween props. Here are a few online possibilities: