Update: The $2.49 sale is only running for a few hours--it ends today at 2PM PDT--so act fast.
"The Terrifying Team Fortress Haunted Hallowe'en Special" brings exploding pumpkins, candy and five achievements that unlock "Mildly Disturbing Halloween Hats," along with Harvest, a new community-made King of the Hill map from Sean "Heyo" Cutin.
The new map is haunted by "the restless spirit of Zepheniah Mann," who "will scare senseless any player unlucky enough to cross his spectral path, rendering them temporarily helpless with fear!"
The criteria for earning the five new "scarechievements" are unknown, though their names--Candy Coroner, Scared Stiff, Ghoastly Gibus Grab, Costume Contest, Attack o' Lantern--provide some not-so-subtle hints.
Team Fortress 2 PC players will get the "pumpkin patch" later today, with the festivities running through November 2. Thanks to Smurfy and Masem for the tips.