This is a Fear Factor like game that you can play at your Halloween party. It will take some preparation, but it's well worth it.
What you do is, prepare a few scary, freaky or stomach turning challenges and see, if your guests are willing to do them. As an incentive, to get more participants, you can get some small Halloween themed prizes.
When creating your challenges, use your imagination. Just to make things easier for you, here are a few ideas...
This is a classic. Peal some grapes and put them in a bowl. They should have the same feel as eyeballs. Blindfold your contestants and tell them to fish out an object. And don't forget to mention that the bowl is filled with cow eyeballs(or if they are really gullible, human eyeballs:)).
Get a box and cut out a hole big enough to fit a hand through, but not big enough to let too much light in(you want to keep the content a secret). Tell your contestants to put their hand in and fish out some object. But, before you start, put one or two mice in the box(clean, healthy mice from a pet store).
The name should be self-explanatory. Make some disgusting looking dishes and see who will dare to eat them(for example, make a brain like dish and tell your contestants it's actual brain). You could also go more authentic and actually make something that truly is horrible to eat, but remember that it actually has to be edible and safe to eat.
Use a closet or a small dark room. It should be in complete darkness. Fill it with spider web like substance(you can buy spider web sprays at gag stores). Tell your contestants that you have actual spiders in that room and that they have to find some object in complete darkness. You can also put some plastic spiders inside for good measure, then listen to them scream when they entangle themselves in "spider webs".
Set up a remote control screen in a completely dark room. Tell your contestants that they have to look for something inside. After one minute in the room remotely turn on the screen with a horrible ghost/zombie face on it, accompanied with a screeching scream. See who runs out the fastest.