Some games feature Halloween and use it to present a macabre and seasonal aesthetic in the game. It is also common for MMOs to feature special Halloween events. Common Halloween aesthetics include cauldrons, pumpkins, Jack-o-Lanterns, the undead and occult.
Halloween in Games
The downloadable RPG from Double Fine, Costume Quest takes place entirely on Halloween. In the game the player controls a child who must go from house to house trick-or-treating. At each house there will either be adult who rewards them with candy (the currency in the game), or there will be a monster behind the door. Upon encountering a monster the game goes into a battle mode where the children's costumes become real, so if a child is dressed as a robot, they become an actual robot.
In Guild Wars around the time of Halloween the annual return of the Grand Thorn King from the Underworld is celebrated. The capital cities are redecorated in a Halloween theme, including an evil face appearing on the moon. Players can participate in special Halloween quests and collect limited edition headwear and consumables.
Based around the movie of the same name, the Atari 2600 game Halloween predictably featured the aforementioned holiday.
Rock of Ages
For Halloween 2011, the developers of Rock of Ages added a Jack-o'-Lantern boulder to the game.
Team Fortress 2
Since 2009 the PC and Mac versions of Team Fortress 2 have held a special event around Halloween known as Scream Fortress. Each year new achievements, maps and items have been introduced, with the most notable of items probably being the various masks given to players.
In 2009 the event version of the map Harvest was introduced which added a ghost that would fly over the capture point and temporarily paralyze players. In 2010 an entirely new map called Mann Manor was added which featured hidden present boxes which appeared randomly around the map and gave the players who found it a Halloween mask. The map also featured a boss monster who would randomly appear known as the Horseless Headless Horseman. In 2011 an event version of the map Viaduct called Eyeaduct was added. This map also features present boxes, as well as a new boss known as Monoculus. Players could also be teleported to the underworld where spirits would attempt to kill them, or to loot island where they could obtain a special Halloween item. The maps have also all featured pumpkins which explode when shot, damaging players around them.
The Simpsons Hit & Run
The final level of The Simpsons Hit & Run features the whole of Springfield made over in a Halloween theme as a homage to the Treehouse of Horror episodes of the show. When played on October 31st the main menu of the game also features a Halloween theme.
When the date on the in-game clock is October 31st players may begin to see witches and bats flying over their zoo.
Tim Burton's Nightmare Before Christmas/Kingdom Hearts
The Nightmare Before Christmas franchise is based around a Halloween theme and the games have featured the same aesthetic. The games of the Kingdom Hearts franchise have also featured levels dedicated to The Nightmare Before Christmas which have featured the Halloween theme.
World of Warcraft
From October 18th to 31st World of Warcraft celebrates All Hallow's End. For the Alliance, the celebration is born out of an old harvest festival held in Lordaeron and for the Horde the 31st October marks the day the Forsaken broke away from the control of the Lich King. In-game the capital cities are covered in Halloween decorations and players can fight the Headless Horseman, collect candy from the candy buckets in the various inns across Azeroth, go apple bobbing, and go trick-or-treating. In WoW trick-or-treating involves talking to an innkeeper (this can be done once an hour at most) and them either giving you a treat bag or forcing a costume onto you.