I think the title says it all. But what do you and your group like? Vampires, Were's, Zombies, Skeletons, Traps?
For me we usually take a break on Halloween but our stories tended to be a little dark anyways so it was a nice break. But sometimes we did an undead cleric turn fest or a get out before they kill you maze. Both are fun for one shots or 2-4 adventures that are a break from the main story.
MDC