OK, so for this game you need a lot of patience, and perhaps and ear plug or 2, but I'm sure the kids will love it. First off, describe different types of screams to the kids, so you don't just get the loudest shout they can manage. Here are some good descriptions for different screams:
1. The I'm-in-the-shower-when-someone-scares-me Scream
2. The it's-the-biggest-spider-I've-ever-seen Scream
3. The I-can't-be-loud-because-I'm-being-chased-by-a-man-eating-zombie Scream
4. The I've-just-entered-into-Frankenstein's-lap-and-his-head-is-open Scream
Now that you've given the kids some ideas... have them line up, give them a number, and let 'er rip! For awards, give them descriptions like above for their signature scream.
This is an old favorite-- freeze dance-- but now play it to your favorite Halloween tune. Monster Mash is a good one! The directions are simple. Have all the kids get into the middle of a big room or open space. Tell them they need to continue to dance until the music gets turned off. If they move when it's off, then they're out. For an award, you can give them a mummy oscar statue for best performance (take an old Barbie and wrap it in gauze bandage.)
Instead of just "scariest costume" or "funniest", try to think of unique and creative categories! For instance, best costume for "Who You Would Not Want to Meet in a Dark Alley." Here's some more:
"Most Believable Costume"
"Most Likely to Be Put in Jail"
"Costume Most Likely to Win an Oscar"
For the awards, you can make a mummy Barbie (like mentioned above), or pick up one of these Skeleton Award Trophies at buycostumes.com.
Would love to find out what your favorite Halloween party game is!
P.S., If ya like the artwork here, be sure to check out my Spooky Halloween party invites and Spooky banner... both are posted on etsy store.