Of the many things you can get during Hallow's End, there is one that I find to be extremely entertaining. The Horseman's Horrific Helm (in various updated iterations across the expansions) has an on-use function that is entirely too fun not to use constantly. The model of the helm is also extremely cool. In fact, I'm considering working up a transmog outfit around the model.
It's a plate helmet, so only Paladins, Warriors, and Death Knights can use it. The stats on it are definitely melee dps stats, but don't let that stop you from picking it up, putting it on, and laughing in a truly maniacal way.
As promised, I've even got a video of the helm in action. Bear in mind that this is among my earliest attempts at WoW videos, so if the quality is not to your standards, get over it. It's instructional, man!