I can't believe I forgot to mention this when I saw this thread....
I only discovered it last year, so it holds no nostalgic value for me, but it became in an instant favorite by merit of its weirdness.
Thats right folks, I speak of Santa Claus Conquers the Martians!
If you have not entertained this... uh... "quality" christmas flick..*ahem*.... You are doing yourself a great disservice.
Also if someone already mentioned this I apologize, I forgot to check before posting this. However, even if it were mentioned, IT IS WORTH SAYING AGAIN!!!
EDIT: Strangely enough just about any Monty Python reminds me of christmas for some reason... I don't know why.