Xmas is the time when I have my brother's kids over and one of the things I most look forward to is playing RPGs and BGs with them.
I just found (and ordered) One Night Ultimate Werewolf
Also getting the Power Up expansion to King of Tokyo.
Other games I am considering for this season:
Ghost Stories - seems like it would be fun but may be a little too long (the kids tend to favor quick, easy to learn rules)
Adventurers: Temple of Chac - I already have Pyramid of Horus which they love, so I may get this.
I bought Horus Heresy a couple of months back and am dying to find somebody who wants to play it (the size of the box is intimidating, I must admit). Playing both sides of a game yourself is a little sad :)
Heard good things about Love letter - will look it up