SnowTag
(requires a snowy field)

Setup:
You'll need a fairly good stretch of undisturbed snow for this one. It's great to play in the morning after a nighttime snowfall. Before playing, walk out into the snow and create a grid (or set of paths) by shuffling your feet around. We usually use a grid of interconnecting lines (like making a giant checkerboard).

Play:
This is tag, plain and simple. One person is "it", and the goal is to not let that person tag you. When you are tagged, you are "it". However, you can only walk in the paths made during the setup. If you ever step off the path, you are instantly "it". There is very little cheating on this one, because your footsteps will show up on the snow, and the person who is "it" will be watching.

Optional Rules:
We like to play that there is no passing allowed. This adds another dimension to the game, because if you're between the person who is "it" and someone else, all that other person has to do is stop moving, and you'll be tagged. It makes keeping track of where you are on the grid very important.

After you've played a couple times, try making the grid more interesting. Instead of a simple checkerboard pattern, make trails that turn and crisscross.