Postal 2 I'm sure.

I remember the Duke Xmas thing was an add on. As far as I knew it wasn't available anymore, I mean not legally.

It's included in the Duke3D: Megaton Edition on Steam.

i want a christmas mod for Hatred :C

OY. Well I have nothing against Steam but I'll pass.

Thank you friend. :D
It will be just like the regular game only instead of running down the same street shooting the same person for five hours you'll run down the same snow covered street shooting the same elf for five hours. :P

I remember the original Rise of the Triad having a little easter egg for Christmas...

The GOG version does indeed have a Christmas event, which starts on 12/15, though you can change your computer clock to have it occur at any time. The mobile version of Terraria also has Valentine's Day, St. Patrick's Day, Easter, and Thanksgiving events!

Raptor has a Christmas "event," but it's just the same extra-monsters-event that you can trigger various other ways.

Oh, so many additions!
Thank you all! *hugs*

The Sacred 2 Christmas Island looks really spiffy.

I hear there's a Christmas mod for Gone Home which allows you to get into the house via the chimney. Once inside you have to go around the house spreading holiday cheer in order to entice your morally bankrupt family back home to share the season's tidings.

I just found out that the Grubbins on Ice DLC pack for Costume Quest (which is included in the PC version) also has christmas-like theme. :-)

dmn i forgot theres 1 scary game that ive played over christmas couple of years..

i'll edit if i rmmber... dmnit

edit : ITS [url=https://en.wikipedia.org/wiki/The_Thing_(video_game)]THE THING[/url]

Unreal Tournament -series have some christmas-themed mods/maps/mutators but everything is pretty spread up between various forums, so it is somewhat messed up.

Here's only some..

[url=https://forums.epicgames.com/threads/978850-StaticMesh-Map-pack-Unreal-Christmas-tree-and-pickup-bases-(updated)][Mutator/Map pack] Unreal Christmas tree and pickup bases[/url]
Christmas Maps and Mutators for UT2004
Christmas mods skinmaps - XMASLights, Capture The Tree, Nude XMAS Themed flags, etc..

Problem with these are that there's no guarantee if the zip/rar-package links work anymore -> might need to find mod repository or somekind of site that has archived stuff.
Another problem is that one should check for what UT specific pack is.. Oh well..
At least those two Epic Games forum threads specify that they are for UT2004.

hmm...

Viscera Cleanup Detail is not on gOg yet.

I just dug up the link in here for a great Lemmings clone that has Christmas Lemmins.