A Light Show? What do you mean by that? When I hear "Light Show", I think of a laser light show, but how can you have that at your house? O.o
How about a scavenger hunt? I don't know where you live, but we used to do those around our blocks. Either everyone has to collect little things, or they can take pictures of the items from their lists. Everyone gets into groups with a disposable camera (because they're cheap and one camera per group). Then your mother or someone can develop the pictures at one of those 1-Hour photo places and you can judge the results later during the party. Another nice place to hold a scavenger hunt is at a mall or something, but try to keep everyone under control and not too rowdy.
I always like those "What's in this box?" Halloween games. You put items in different boxes and the guests reach in and write what they think it is on a sheet of paper. You can probably Google a list of cool items, like peeled grapes, soggy pretzel sticks, jello, wet spaghetti, etc. This can also be fun as part of a scary story. Everyone can sit in a circle in the dark with a flashlight for the storyteller. The storyteller starts the story which at one point must involve finding or touching objects. When the story gets to one of these sections, the storyteller passes around a bowl of whatever item feels like that body part (peeled grapes for eyes, wet spaghetti for brains, etc.). Of course, it has to have a scary ending. Something you can toss at everyone at the end works good, like silly string (not recommended if some people have glasses and it can be very messy) or something else you can toss at everyone. Just make sure it is something softish so no one gets hurt.
Something I always loved at Halloween parties is fortunetelling. You can have someone set up to do card readings with a simple deck of cards. There are some really easy readings that only use like 3 cards per person, (not hard to do). It's fun to hear everyone's fortune. You can either have this done in front of everyone or have the person who is going to be read go into a seperate room.
Halloween pinatas are fun. You can fill them with all sorts of Halloween goodies. If you want, everyone can even wear a witches hat (and a blindfold, of course) and use a broom stick to hit the pinata to give it a Hallween feel.
One year, my friends and I blew up balloons (orange and black for Halloween) and placed little gifts in them. Everyone left the room and we put out all the balloons. Then we'd let them loose. They'd have to pop the balloons to get the gifts. It was loads of fun.
You can also get little gourds and have everyone decorate them using markers, construction paper, yarn, glitter, whatever. Then have everyone vote on which they like the best. (This can also be done with balloons or Halloween shaped cookies(using frosting and sprinkles, or course
)).
A murder mystery can be fun. You can make up the story and tell the guests when they arrive. One person will be designated as the "murderer". Who this is will be kept secret. Throughout the party, the "murderer" will "kill" guests when no one else is looking. The "murdered" guests pin something on their shirts or something to designate them as "dead" (stickers are good as well, but may come off during the party, you can also use something else like a spider ring or something, but each "dead" must have the same item). They cannot speak about the mystery at all, but can participate in the rest of the party. At several points throughout the party, everyone will gather and discuss who they think the "murderer" is. Then each guest writes their guess on a piece of paper and places it in a box (empty tissue box or whatever). They votes are tallied up and if the murderer was guessed by majority, everyone gets a prize. If not, it continues until the next time, with people being "murderer" in the meanwhile. If no one guesses who the "murderer" is by the time a certain number of people are left (a low number like two, three, or four), then the "murderer" gets an extra special prize. Of course, the "dead" do not get to vote or be in the room when the guests discuss the "murderer". Also, decide beforehand how many guests are to "die" inbetween meetings.
That's all I can think of for now. We used to do a lot of other things as well, but I don't know if you're into that sort of thing (seances, ouija board, and such). Here's a site with a lot of games ideas:
http://www.partygameideas.com/halloweengames.htm
A lot of the games there were for kids, but there were some interesting ones for older guests as well.
I used to hold a Halloween party every year. We used to do a lot more, but I can't remember at the moment. If I can think of anything else, I'll post again.