Embrace your inner child and take advantage of that powdery white stuff: have a real, drag-out snowball fight. (Think of the fight from Elf.) Give each team a little time to make snowballs, blow a whistle, and make sure to have a referee. Serve wassail afterward, and cozy up at home and watch one of those Christmas movies you couldn’t get to during your marathon on Day 4.
But, if you’re not near snow (or you don’t want to get cold), you still have some really fun options:
Have an indoor snowball fight with stuffed snowballs. Plush snowballs are widely available; see one example at Amazon.com. Some people in colder climates even prefer these “snowball” fights to the real thing.
Use jumbo marshmallows and powdered sugar or flour to create “snowballs.” Go outside, and have at it! You can even try to give points afterward to the most successful team, judging on who’s more powdered up. If you have a room in your house that you don’t mind getting messy, turn over the furniture for barricades and have the fight there.
And, if you REALLY don't mind getting messy and sticky outside: Get some cheap gallons of vanilla ice cream and scoop it out into well-formed balls. Re-freeze them, take them outside, and don't look back.
Most of all, have fun! It’s one of winter’s easiest ways to work up a sweat.