Usually at Halloween parties I attend in the costume of "that guy who drinks all the beer and eats all the chips and man does he ever stop???" The first several minutes of the party are spent ooh-ing and aah-ing over costumes both clever ("I'm going as my husband's dashed hopes and dreams!") and common ("I'm going as a sexy vampiric nurse with a cowboy hat! Yes, I need to clean out my closet..."). You can always count on one girl in fishnet stockings, and one guy with no shirt on.
When we were little and these parties were chaperoned, you could also count on the hostess (no man ever chaperones his kid's Halloween party, that's just not a manly thing to do!) getting rid of all of her cold spaghetti and grapes (which, in the dark, are supposedly guts and eyeballs) and coming up with games like "try not to break our stuff" and "stop poking me with that damn fake spear". Some kid's costume gets ripped, some kid starts crying, and it's usually over early in the day. When we're teenagers, we're up to mischief--eggings and toilet paperings create their own reign of terror on the lands!--but then we get to an age where we're out of the house, able to drink legally, and then the parties about yet again. But what activities can you participate in at Halloween parties as an adult? Passing around goo and pretending it's brains doesn't work anymore. Here are some suggestions:
1) A prize for whoever can eat the oldest thing still in the host's fridge. Scary!
2) A prize for the female guest who actually dressed modestly.
3) A game of "who wants to check to see if that's really a gas leak".
4) A ritual beating for the guy who dripped candle wax on the stereo speakers.
5) A murder mystery! To make it more authentic, invite an actual paroled murderer and have him wait out back by the beer cooler and send guests out to get beers one by one. Also helps if you have an amateur detective--preferably with a Belgian accent!--as another guest.