Christmas quests hmmm, Could be just like that halloween quest, you bring an NPC body parts but now instead of body parts you bring "Santa" candy that snowmen drops, and like a few snowballs, a santa hat, and things like that, or he could give you like a mission were you are suppose to kill someone with a snowball or destroy some snowmens,
this might be an EVIL SANTA :O..
I will edit more ideas if nobody else doesen't
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EDIT: I was thinking of a quest like, First a Santa NPC tells you to go to his little elfs and give them a letter the santa gives you, and the elfs tells you to do something like "go get us some materials for our toy making" and then when you bring it back to them they tells you to go back to santa, and santa tells you do something else, This quest can contain 5 missions and the prize would be like some sort of candy that improves your gun speed or whatever ;O