Ok, you mean other than just get kind of wasted and talk? Sure, we know about the usuals here: apple bobbing, costume contests, maybe squash bowling? But we’re betting Homies have some AMAZING Halloween party activities.
Zombie races? Jack o’ lantern puke-fests? SPILL THE IDEAS, HOMIES!
I know someone’s already talked about games a little, but to add to that…I just found a cheap game at Goodwill that I’m pretty sure I played as a kid, and it comes with a VHS tape that goes along with it! It’s like creepy board game meets scary movie, if I recall correctly. But aside from that, old murder mystery dinner party games could be cool, too, if you have a crowd that would be into it (though I imagine they would be a little more structured).
For loosely structured stuff, what about some trivia? You could easily come up with some trivia questions and toss out candy to people who answer correctly. We’ve done this at parties with varying degrees of success, and usually spawns offshoot conversations, thereby advancing socializing.
We have a fair amount of gatherings, and usually if there’s just one sort of “bonding” moment for the group, it tends to get the ball rolling for things to take off on their own: even if that’s just watching us make a cool cocktail for everyone to try simultaneously, it sparks conversation. In my experience, the cheesier the group interaction, the better, but that obviously depends on your crowd, so your mileage may vary.