The subject of this article or section is part of Hallow's End, a seasonal event that lasts two weeks. Once the event has run its course, this will no longer be available until next year, but there are no guarantees.
Use: Jam onto your head, or throw at your friends!
The Weighted Jack-o'-Lantern item, when used on either another player or yourself, changes your head to a pumpkin (just like the Hallowed Helm effect).
It is also given as a reward for the fire fighting daily quest during Hallow's End.
For the Check Your Head Hallow's End World Event achievement, you have to use a Weighted Jack-o'-Lantern on each player race; gnome, blood elf, draenei, dwarf, human, night elf, orc, tauren, troll, and undead, ten in all.