I'm always a fan of Christmas weeks, and seeing the sets decked out with holiday decorations. Not so sure if I have a favorite, though I love the clip from Woolery's Wheel (1979 or '80), where a lady won a new Mazda hatchback during the main game. The fact that it was Christmas was honestly more of a coincidence, but it was still a lot of fun to watch.
If there's a least favorite, I'd prolly go with Bergeron's Squares c. 2001. It's one thing when the adult celebrities spout off one-liners, but with children doing so, it just seemed weird. It's along the same lines of when kids would pontificate the survey questions on Card Sharks.
One thing I miss on game shows nowadays is hearing an instrumental of Sleigh Ride playing over the credits. I think TPiR may still do it, but it's been a few years since I've seen a Christmas episode.