If you're looking for a simple, fun Windows Phone game, take a look at SantaRacer. The game was recently updated to version 2.0 with a new game engine under the hood and improved graphics that include snow fall.
SantaRacer has you guiding Santa and his sleight up a hill collecting presents and avoiding flying rocks along the way. If you hit a rock, you lose a reindeer. Run out of time or reindeers and the game's over. SantaRacer is a fun game to pass the time with and has a bit of challenge.