Come up with a story concept, the theme is Halloween. It can be a short story concept it can be the concept for a Robert Jordan length series. Don't actually write the story, just present what you come up with from the top of your head. Just as a quick fun exercise to show how different and alike we are as writer at this community.
Setting aside my stupid angsty gay romance drama set in a bat-infested house that I was writing earlier (lol, Halloween is on my mind too), um... I'd almost certainly look at paganism or wicca for an actual fantasy Halloween story instead of just one set on that date with plenty of references to Halloween-y things. Perhaps a story in my teen fantasy series where I already know all the rules of magic I've come up with, so could just have a typical "oh noes the veil between worlds is too thin, bad stuff is happening!" plot that those tend to have, since they're all about meddling with magic in the same way other teenagers vandalise bus shelters. That wouldn't require too much plotting, just a couple of events/monsters to worry about, and I'd probably focus on the personal side of it anyway, so Halloween would just provide the atmosphere and some action on the side.
I would go for someone actually fresh with grief on Halloween night, taking offence, getting anger and growing bitter at the celebration. An old lady perhaps as the main person, who just lost her grown child. Describe how she puts out with pranking teens and rude children as well as a few (in her eyes) kind children and teens. And let the reader follow the old ladies mind as she begin to consider go out trick and treating on her own, perhaps with a knife or perhaps with poisoned candy separating the nice kids from the naughty ones. And leave it at that, letting the reader decide on the old lady went on a killing spree or not. A quiet story, meant to show as the old lady both in a sympathetic and a less flattering night, letting the reader decide if she ultimately was a good person daydreaming some dark thoughts or someone actually able to commit murder.
Hmmm... since I'm already working on a vampire story myself I w ould probably play around with them a little: imagine a modern setting my four characters (two twin brother, pure blood vampires and their fledglings) would all be home in their large mansion in the outskirts of a small village. Silas (the youngest fledgling) is bored and wants to go and celebrate Halloween. Although the others aren't too enthusiastic about it they play along with Silas' idea (as they always do). They'll go trick or treating (I would have to do some research on that phenomenom, since we don't have Halloween in Holland) dressed up like stereotypical vampires complete with fake teeth. They all have a good laugh, and no one is the wiser they are true vampires. that's what just came to mind. It was fun to think something up like that on such short notice.
A mysterious man shows up trick or treating and gives a crytic message which leads the main character on the road to a stratling discovery about his own existence, finding that his quiet suburban world is in fact a carefully controlled and monitored Human colonisation on a foreign planet. He escapes the fake reality and discovers that the planet is full of monsters that would make Halloween ghosties quake in their boots.
I love campy halloween stuff. SO I was thinking a good old fashioned TIm Currey esc, giant game of clue. The game could involve important towns folk or well anyone really. The main characters being a group of (you guessed it) campy teenagers all flinging around a mess of cliched halloween spoofed up phrases. And of course.. the creepy house at the edge of town complete with it's own grave yard. Hey... sometimes camp is fun
As Halloween approaches, the main character is reminded of his dead friend and mentor, who he hasn't thought of in many years. Events conspire to leave him alone on Halloween, and confront him with his mentor's dying wish - to finish the job that killed him.
