Actually, on some streets this would be useful every day.
Cyclists are often defenceless creatures, but in the UK, they actually have an insurance company behind them, offering this "Halloween bicycle... equipped with a range of non-standard accessories including an electric chainsaw, flamethrower, automatic smoke screen dispenser, iridium splatter shield and axe."
Should Halloween 2017 herald a full-blown zombie apocalypse, remember to avoid cars as they attract attention and rely on expensive petrol. Instead, try customising your bicycle as it doesn’t rely on oil, allows you to easily exorcise and is stealthy (it’s a well-known fact that zombies are attracted by noise).
ETA doesn't say how much extra their insurance costs when you have a bike like this, which is a shame; this would be useful on many streets on any day of the year.